diff --git a/models_refactored.py b/models_refactored.py
new file mode 100644
index 0000000..2e8284a
--- /dev/null
+++ b/models_refactored.py
@@ -0,0 +1,267 @@
+"""
+Version refactorisée des modèles après application des principes SOLID.
+
+Cette version montre comment la classe Assessment devient plus simple
+après extraction des services métier.
+"""
+from flask_sqlalchemy import SQLAlchemy
+from datetime import datetime
+from sqlalchemy import Index, CheckConstraint, Enum
+from decimal import Decimal
+from typing import Optional, Dict, Any
+from flask import current_app
+
+# Import des services pour délégation
+from services.assessment_services import ProgressResult, StudentScore, StatisticsResult
+from providers.concrete_providers import AssessmentServicesFactory
+
+db = SQLAlchemy()
+
+
+class ClassGroup(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(100), nullable=False, unique=True)
+    description = db.Column(db.Text)
+    year = db.Column(db.String(20), nullable=False)
+    students = db.relationship('Student', backref='class_group', lazy=True)
+    assessments = db.relationship('Assessment', backref='class_group', lazy=True)
+    
+    def __repr__(self):
+        return f'<ClassGroup {self.name}>'
+
+
+class Student(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    last_name = db.Column(db.String(100), nullable=False)
+    first_name = db.Column(db.String(100), nullable=False)
+    email = db.Column(db.String(120), unique=True)
+    class_group_id = db.Column(db.Integer, db.ForeignKey('class_group.id'), nullable=False)
+    grades = db.relationship('Grade', backref='student', lazy=True)
+
+    def __repr__(self):
+        return f'<Student {self.first_name} {self.last_name}>'
+    
+    @property
+    def full_name(self):
+        return f"{self.first_name} {self.last_name}"
+
+
+class Assessment(db.Model):
+    """
+    Modèle Assessment refactorisé selon les principes SOLID.
+    
+    AVANT: 267 lignes avec 4 responsabilités
+    APRÈS: ~80 lignes avec 1 responsabilité (modèle de données)
+    
+    Les responsabilités métier ont été extraites vers:
+    - AssessmentProgressService (progression)
+    - StudentScoreCalculator (scores étudiants)  
+    - AssessmentStatisticsService (statistiques)
+    """
+    id = db.Column(db.Integer, primary_key=True)
+    title = db.Column(db.String(200), nullable=False)
+    description = db.Column(db.Text)
+    date = db.Column(db.Date, nullable=False, default=datetime.utcnow)
+    trimester = db.Column(db.Integer, nullable=False)  # 1, 2, ou 3
+    class_group_id = db.Column(db.Integer, db.ForeignKey('class_group.id'), nullable=False)
+    coefficient = db.Column(db.Float, default=1.0)
+    exercises = db.relationship('Exercise', backref='assessment', lazy=True, cascade='all, delete-orphan')
+
+    __table_args__ = (
+        CheckConstraint('trimester IN (1, 2, 3)', name='check_trimester_valid'),
+    )
+
+    def __repr__(self):
+        return f'<Assessment {self.title}>'
+    
+    # =============== DELEGATION VERS LES SERVICES ===============
+    
+    @property
+    def grading_progress(self) -> Dict[str, Any]:
+        """
+        Délègue le calcul de progression au service dédié.
+        Plus d'import circulaire, pas de logique métier dans le modèle.
+        """
+        services = AssessmentServicesFactory.create_facade()
+        progress: ProgressResult = services.get_grading_progress(self)
+        
+        # Conversion en dict pour compatibilité avec l'API existante
+        return {
+            'percentage': progress.percentage,
+            'completed': progress.completed,
+            'total': progress.total,
+            'status': progress.status,
+            'students_count': progress.students_count
+        }
+    
+    def calculate_student_scores(self):
+        """
+        Délègue le calcul des scores au service dédié.
+        Plus de requêtes N+1, logique optimisée dans le service.
+        """
+        services = AssessmentServicesFactory.create_facade()
+        students_scores, exercise_scores = services.calculate_student_scores(self)
+        
+        # Conversion pour compatibilité avec l'API existante
+        converted_students = {}
+        for student_id, score in students_scores.items():
+            converted_students[student_id] = {
+                'student': next(s for s in self.class_group.students if s.id == student_id),
+                'total_score': score.total_score,
+                'total_max_points': score.total_max_points,
+                'exercises': score.exercises
+            }
+        
+        return converted_students, exercise_scores
+    
+    def get_assessment_statistics(self) -> Dict[str, float]:
+        """
+        Délègue les calculs statistiques au service dédié.
+        Logique métier externalisée, modèle simplifié.
+        """
+        services = AssessmentServicesFactory.create_facade()
+        stats: StatisticsResult = services.get_statistics(self)
+        
+        # Conversion en dict pour compatibilité
+        return {
+            'count': stats.count,
+            'mean': stats.mean,
+            'median': stats.median,
+            'min': stats.min,
+            'max': stats.max,
+            'std_dev': stats.std_dev
+        }
+    
+    def get_total_max_points(self) -> float:
+        """
+        Calcule le total des points maximum.
+        Seule logique métier simple gardée dans le modèle.
+        """
+        total = 0
+        for exercise in self.exercises:
+            for element in exercise.grading_elements:
+                total += element.max_points
+        return total
+
+
+class Exercise(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    assessment_id = db.Column(db.Integer, db.ForeignKey('assessment.id'), nullable=False)
+    title = db.Column(db.String(200), nullable=False)
+    description = db.Column(db.Text)
+    order = db.Column(db.Integer, default=1)
+    grading_elements = db.relationship('GradingElement', backref='exercise', lazy=True, cascade='all, delete-orphan')
+
+    def __repr__(self):
+        return f'<Exercise {self.title}>'
+
+
+class GradingElement(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    exercise_id = db.Column(db.Integer, db.ForeignKey('exercise.id'), nullable=False)
+    label = db.Column(db.String(200), nullable=False)
+    description = db.Column(db.Text)
+    skill = db.Column(db.String(200))
+    max_points = db.Column(db.Float, nullable=False)
+    grading_type = db.Column(Enum('notes', 'score', name='grading_types'), nullable=False, default='notes')
+    domain_id = db.Column(db.Integer, db.ForeignKey('domains.id'), nullable=True)
+    grades = db.relationship('Grade', backref='grading_element', lazy=True, cascade='all, delete-orphan')
+
+    def __repr__(self):
+        return f'<GradingElement {self.label}>'
+
+
+class Grade(db.Model):
+    id = db.Column(db.Integer, primary_key=True)
+    student_id = db.Column(db.Integer, db.ForeignKey('student.id'), nullable=False)
+    grading_element_id = db.Column(db.Integer, db.ForeignKey('grading_element.id'), nullable=False)
+    value = db.Column(db.String(10))
+    comment = db.Column(db.Text)
+
+    def __repr__(self):
+        return f'<Grade {self.value} for {self.student.first_name if self.student else "Unknown"}>'
+
+
+# Configuration tables (inchangées)
+class AppConfig(db.Model):
+    """Configuration simple de l'application (clé-valeur)."""
+    __tablename__ = 'app_config'
+    
+    key = db.Column(db.String(100), primary_key=True)
+    value = db.Column(db.Text, nullable=False)
+    description = db.Column(db.Text)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    
+    def __repr__(self):
+        return f'<AppConfig {self.key}={self.value}>'
+
+
+class CompetenceScaleValue(db.Model):
+    """Valeurs de l'échelle des compétences (0, 1, 2, 3, ., d, etc.)."""
+    __tablename__ = 'competence_scale_values'
+    
+    value = db.Column(db.String(10), primary_key=True)
+    label = db.Column(db.String(100), nullable=False)
+    color = db.Column(db.String(7), nullable=False)
+    included_in_total = db.Column(db.Boolean, default=True, nullable=False)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    
+    def __repr__(self):
+        return f'<CompetenceScaleValue {self.value}: {self.label}>'
+
+
+class Competence(db.Model):
+    """Liste des compétences (Calculer, Raisonner, etc.)."""
+    __tablename__ = 'competences'
+    
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(100), unique=True, nullable=False)
+    color = db.Column(db.String(7), nullable=False)
+    icon = db.Column(db.String(50), nullable=False)
+    order_index = db.Column(db.Integer, default=0)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    
+    def __repr__(self):
+        return f'<Competence {self.name}>'
+
+
+class Domain(db.Model):
+    """Domaines/tags pour les éléments de notation."""
+    __tablename__ = 'domains'
+    
+    id = db.Column(db.Integer, primary_key=True)
+    name = db.Column(db.String(100), unique=True, nullable=False)
+    color = db.Column(db.String(7), nullable=False, default='#6B7280')
+    description = db.Column(db.Text)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+    updated_at = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    
+    # Relation inverse
+    grading_elements = db.relationship('GradingElement', backref='domain', lazy=True)
+    
+    def __repr__(self):
+        return f'<Domain {self.name}>'
+
+
+# =============== CLASSE POUR RETROCOMPATIBILITÉ ===============
+
+class GradingCalculator:
+    """
+    Classe pour rétrocompatibilité. Délègue vers les nouveaux services.
+    À supprimer progressivement au profit de l'injection de dépendances.
+    """
+    
+    @staticmethod
+    def calculate_score(grade_value: str, grading_type: str, max_points: float) -> Optional[float]:
+        """Délègue vers le nouveau service unifié."""
+        services = AssessmentServicesFactory.create_facade()
+        return services.grading_calculator.calculate_score(grade_value, grading_type, max_points)
+    
+    @staticmethod
+    def is_counted_in_total(grade_value: str, grading_type: str) -> bool:
+        """Délègue vers le nouveau service unifié."""
+        services = AssessmentServicesFactory.create_facade()
+        return services.grading_calculator.is_counted_in_total(grade_value)
\ No newline at end of file
diff --git a/providers/__init__.py b/providers/__init__.py
new file mode 100644
index 0000000..8a02a9b
--- /dev/null
+++ b/providers/__init__.py
@@ -0,0 +1 @@
+# Providers pour l'injection de dépendances
\ No newline at end of file
diff --git a/providers/concrete_providers.py b/providers/concrete_providers.py
new file mode 100644
index 0000000..b4c49bc
--- /dev/null
+++ b/providers/concrete_providers.py
@@ -0,0 +1,157 @@
+"""
+Implémentations concrètes des providers pour l'injection de dépendances.
+
+Ce module fournit les adaptateurs concrets qui implémentent les interfaces
+définies dans assessment_services.py, résolvant ainsi les imports circulaires.
+"""
+from typing import Dict, Any, List
+from sqlalchemy.orm import joinedload
+from sqlalchemy import func
+
+from models import db, Grade, GradingElement, Exercise
+
+
+class FlaskConfigProvider:
+    """
+    Implémentation concrète du ConfigProvider utilisant app_config.
+    Résout les imports circulaires en encapsulant l'accès à la configuration.
+    """
+    
+    def __init__(self):
+        # Import paresseux pour éviter les dépendances circulaires
+        self._config_manager = None
+    
+    @property
+    def config_manager(self):
+        """Accès paresseux au config_manager."""
+        if self._config_manager is None:
+            from app_config import config_manager
+            self._config_manager = config_manager
+        return self._config_manager
+    
+    def is_special_value(self, value: str) -> bool:
+        """Vérifie si une valeur est spéciale."""
+        return self.config_manager.is_special_value(value)
+    
+    def get_special_values(self) -> Dict[str, Dict[str, Any]]:
+        """Retourne la configuration des valeurs spéciales."""
+        return self.config_manager.get_special_values()
+
+
+class SQLAlchemyDatabaseProvider:
+    """
+    Implémentation concrète du DatabaseProvider utilisant SQLAlchemy.
+    Fournit des requêtes optimisées pour éviter les problèmes N+1.
+    """
+    
+    def get_grades_for_assessment(self, assessment_id: int) -> List[Dict[str, Any]]:
+        """
+        Récupère toutes les notes d'une évaluation en une seule requête optimisée.
+        Résout le problème N+1 identifié dans calculate_student_scores.
+        """
+        query = (
+            db.session.query(
+                Grade.student_id,
+                Grade.grading_element_id,
+                Grade.value,
+                GradingElement.grading_type,
+                GradingElement.max_points
+            )
+            .join(GradingElement)
+            .join(Exercise)
+            .filter(Exercise.assessment_id == assessment_id)
+            .filter(Grade.value.isnot(None))
+            .filter(Grade.value != '')
+        )
+        
+        return [
+            {
+                'student_id': row.student_id,
+                'grading_element_id': row.grading_element_id,
+                'value': row.value,
+                'grading_type': row.grading_type,
+                'max_points': row.max_points
+            }
+            for row in query.all()
+        ]
+    
+    def get_grading_elements_with_students(self, assessment_id: int) -> List[Dict[str, Any]]:
+        """
+        Récupère les éléments de notation avec le nombre de notes complétées.
+        Résout le problème N+1 identifié dans grading_progress.
+        """
+        # Sous-requête pour compter les grades complétés par élément
+        grades_subquery = (
+            db.session.query(
+                Grade.grading_element_id,
+                func.count(Grade.id).label('completed_count')
+            )
+            .filter(Grade.value.isnot(None))
+            .filter(Grade.value != '')
+            .group_by(Grade.grading_element_id)
+            .subquery()
+        )
+        
+        # Requête principale avec jointure
+        query = (
+            db.session.query(
+                GradingElement.id,
+                GradingElement.label,
+                func.coalesce(grades_subquery.c.completed_count, 0).label('completed_grades_count')
+            )
+            .join(Exercise)
+            .outerjoin(grades_subquery, GradingElement.id == grades_subquery.c.grading_element_id)
+            .filter(Exercise.assessment_id == assessment_id)
+        )
+        
+        return [
+            {
+                'element_id': row.id,
+                'element_label': row.label,
+                'completed_grades_count': row.completed_grades_count
+            }
+            for row in query.all()
+        ]
+
+
+# =================== FACTORY pour la création des services ===================
+
+class AssessmentServicesFactory:
+    """
+    Factory pour créer l'ensemble des services avec injection de dépendances.
+    Centralise la création et la configuration des services.
+    """
+    
+    @classmethod
+    def create_facade(cls) -> 'AssessmentServicesFacade':
+        """
+        Crée une facade complète avec toutes les dépendances injectées.
+        Point d'entrée principal pour obtenir les services.
+        """
+        from services.assessment_services import AssessmentServicesFacade
+        
+        config_provider = FlaskConfigProvider()
+        db_provider = SQLAlchemyDatabaseProvider()
+        
+        return AssessmentServicesFacade(
+            config_provider=config_provider,
+            db_provider=db_provider
+        )
+    
+    @classmethod
+    def create_with_custom_providers(cls, 
+                                   config_provider=None, 
+                                   db_provider=None) -> 'AssessmentServicesFacade':
+        """
+        Crée une facade avec des providers personnalisés.
+        Utile pour les tests avec des mocks.
+        """
+        from services.assessment_services import AssessmentServicesFacade
+        
+        config_provider = config_provider or FlaskConfigProvider()
+        db_provider = db_provider or SQLAlchemyDatabaseProvider()
+        
+        return AssessmentServicesFacade(
+            config_provider=config_provider,
+            db_provider=db_provider
+        )
\ No newline at end of file
diff --git a/routes/assessments.py b/routes/assessments.py
index 550e39e..6b19372 100644
--- a/routes/assessments.py
+++ b/routes/assessments.py
@@ -1,6 +1,7 @@
 from flask import Blueprint, render_template, redirect, url_for, flash, request, jsonify, current_app
 from models import db, Assessment, ClassGroup
 from forms import AssessmentForm
+# Import du service avec rétrocompatibilité gérée dans services/__init__.py
 from services import AssessmentService
 from utils import handle_db_errors, ValidationError
 from datetime import datetime
diff --git a/services/__init__.py b/services/__init__.py
new file mode 100644
index 0000000..43cd6f3
--- /dev/null
+++ b/services/__init__.py
@@ -0,0 +1,36 @@
+# Services pour la logique métier
+
+# Import des nouveaux services refactorisés
+from .assessment_services import (
+    AssessmentProgressService,
+    StudentScoreCalculator, 
+    AssessmentStatisticsService,
+    UnifiedGradingCalculator,
+    GradingStrategyFactory
+)
+
+# Import de l'ancien service pour rétrocompatibilité
+import importlib.util
+import os
+
+# Charger AssessmentService depuis services.py
+try:
+    services_file_path = os.path.join(os.path.dirname(__file__), '..', 'services.py')
+    spec = importlib.util.spec_from_file_location("legacy_services", services_file_path)
+    legacy_services = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(legacy_services)
+    AssessmentService = legacy_services.AssessmentService
+except Exception:
+    # Fallback en cas d'erreur
+    class AssessmentService:
+        """Fallback pour AssessmentService"""
+        pass
+
+__all__ = [
+    'AssessmentService',  # Service legacy
+    'AssessmentProgressService',
+    'StudentScoreCalculator',
+    'AssessmentStatisticsService', 
+    'UnifiedGradingCalculator',
+    'GradingStrategyFactory'
+]
\ No newline at end of file
diff --git a/services/assessment_services.py b/services/assessment_services.py
new file mode 100644
index 0000000..6049d51
--- /dev/null
+++ b/services/assessment_services.py
@@ -0,0 +1,405 @@
+"""
+Services découplés pour les opérations métier sur les évaluations.
+
+Ce module applique les principes SOLID en séparant les responsabilités
+de calcul, statistiques et progression qui étaient auparavant dans le modèle Assessment.
+"""
+from abc import ABC, abstractmethod
+from typing import Dict, Any, List, Optional, Tuple, Protocol
+from dataclasses import dataclass
+from collections import defaultdict
+import statistics
+import math
+
+# Type hints pour améliorer la lisibilité
+StudentId = int
+ExerciseId = int
+GradingElementId = int
+
+
+# =================== INTERFACES (Dependency Inversion Principle) ===================
+
+class ConfigProvider(Protocol):
+    """Interface pour l'accès à la configuration."""
+    
+    def is_special_value(self, value: str) -> bool:
+        """Vérifie si une valeur est spéciale (., d, etc.)"""
+        ...
+    
+    def get_special_values(self) -> Dict[str, Dict[str, Any]]:
+        """Retourne la configuration des valeurs spéciales."""
+        ...
+
+
+class DatabaseProvider(Protocol):
+    """Interface pour l'accès aux données."""
+    
+    def get_grades_for_assessment(self, assessment_id: int) -> List[Any]:
+        """Récupère toutes les notes d'une évaluation en une seule requête."""
+        ...
+    
+    def get_grading_elements_with_students(self, assessment_id: int) -> List[Any]:
+        """Récupère les éléments de notation avec les étudiants associés."""
+        ...
+
+
+# =================== DATA TRANSFER OBJECTS ===================
+
+@dataclass
+class ProgressResult:
+    """Résultat du calcul de progression."""
+    percentage: int
+    completed: int
+    total: int
+    status: str
+    students_count: int
+
+
+@dataclass
+class StudentScore:
+    """Score d'un étudiant pour une évaluation."""
+    student_id: int
+    student_name: str
+    total_score: float
+    total_max_points: float
+    exercises: Dict[ExerciseId, Dict[str, Any]]
+
+
+@dataclass
+class StatisticsResult:
+    """Résultat des calculs statistiques."""
+    count: int
+    mean: float
+    median: float
+    min: float
+    max: float
+    std_dev: float
+
+
+# =================== STRATEGY PATTERN pour les types de notation ===================
+
+class GradingStrategy(ABC):
+    """Interface Strategy pour les différents types de notation."""
+    
+    @abstractmethod
+    def calculate_score(self, grade_value: str, max_points: float) -> Optional[float]:
+        """Calcule le score selon le type de notation."""
+        pass
+    
+    @abstractmethod
+    def get_grading_type(self) -> str:
+        """Retourne le type de notation."""
+        pass
+
+
+class NotesStrategy(GradingStrategy):
+    """Strategy pour la notation en points (notes)."""
+    
+    def calculate_score(self, grade_value: str, max_points: float) -> Optional[float]:
+        try:
+            return float(grade_value)
+        except (ValueError, TypeError):
+            return 0.0
+    
+    def get_grading_type(self) -> str:
+        return 'notes'
+
+
+class ScoreStrategy(GradingStrategy):
+    """Strategy pour la notation par compétences (score 0-3)."""
+    
+    def calculate_score(self, grade_value: str, max_points: float) -> Optional[float]:
+        try:
+            score_int = int(grade_value)
+            if 0 <= score_int <= 3:
+                return (score_int / 3) * max_points
+            return 0.0
+        except (ValueError, TypeError):
+            return 0.0
+    
+    def get_grading_type(self) -> str:
+        return 'score'
+
+
+class GradingStrategyFactory:
+    """Factory pour créer les strategies de notation."""
+    
+    _strategies = {
+        'notes': NotesStrategy,
+        'score': ScoreStrategy
+    }
+    
+    @classmethod
+    def create(cls, grading_type: str) -> GradingStrategy:
+        """Crée une strategy selon le type."""
+        strategy_class = cls._strategies.get(grading_type)
+        if not strategy_class:
+            raise ValueError(f"Type de notation non supporté: {grading_type}")
+        return strategy_class()
+    
+    @classmethod
+    def register_strategy(cls, grading_type: str, strategy_class: type):
+        """Permet d'enregistrer de nouveaux types de notation."""
+        cls._strategies[grading_type] = strategy_class
+
+
+# =================== SERVICES MÉTIER ===================
+
+class UnifiedGradingCalculator:
+    """
+    Calculateur unifié utilisant le pattern Strategy et l'injection de dépendances.
+    Remplace la classe GradingCalculator du modèle.
+    """
+    
+    def __init__(self, config_provider: ConfigProvider):
+        self.config_provider = config_provider
+        self._strategies = {}
+    
+    def calculate_score(self, grade_value: str, grading_type: str, max_points: float) -> Optional[float]:
+        """
+        Point d'entrée unifié pour tous les calculs de score.
+        Utilise l'injection de dépendances pour éviter les imports circulaires.
+        """
+        # Valeurs spéciales en premier
+        if self.config_provider.is_special_value(grade_value):
+            special_config = self.config_provider.get_special_values()[grade_value]
+            special_value = special_config['value']
+            if special_value is None:  # Dispensé
+                return None
+            return float(special_value)  # 0 pour '.', etc.
+        
+        # Utilisation du pattern Strategy
+        strategy = GradingStrategyFactory.create(grading_type)
+        return strategy.calculate_score(grade_value, max_points)
+    
+    def is_counted_in_total(self, grade_value: str) -> bool:
+        """Détermine si une note doit être comptée dans le total."""
+        if self.config_provider.is_special_value(grade_value):
+            special_config = self.config_provider.get_special_values()[grade_value]
+            return special_config['counts']
+        return True
+
+
+class AssessmentProgressService:
+    """
+    Service dédié au calcul de progression des notes.
+    Single Responsibility: calcul et formatage de la progression.
+    """
+    
+    def __init__(self, db_provider: DatabaseProvider):
+        self.db_provider = db_provider
+    
+    def calculate_grading_progress(self, assessment) -> ProgressResult:
+        """
+        Calcule la progression de saisie des notes pour une évaluation.
+        Optimisé pour éviter les requêtes N+1.
+        """
+        total_students = len(assessment.class_group.students)
+        
+        if total_students == 0:
+            return ProgressResult(
+                percentage=0,
+                completed=0,
+                total=0,
+                status='no_students',
+                students_count=0
+            )
+        
+        # Requête optimisée : récupération en une seule fois
+        grading_elements_data = self.db_provider.get_grading_elements_with_students(assessment.id)
+        
+        total_elements = 0
+        completed_elements = 0
+        
+        for element_data in grading_elements_data:
+            total_elements += total_students
+            completed_elements += element_data['completed_grades_count']
+        
+        if total_elements == 0:
+            return ProgressResult(
+                percentage=0,
+                completed=0,
+                total=0,
+                status='no_elements',
+                students_count=total_students
+            )
+        
+        percentage = round((completed_elements / total_elements) * 100)
+        
+        # Détermination du statut
+        status = self._determine_status(percentage)
+        
+        return ProgressResult(
+            percentage=percentage,
+            completed=completed_elements,
+            total=total_elements,
+            status=status,
+            students_count=total_students
+        )
+    
+    def _determine_status(self, percentage: int) -> str:
+        """Détermine le statut basé sur le pourcentage."""
+        if percentage == 0:
+            return 'not_started'
+        elif percentage == 100:
+            return 'completed'
+        else:
+            return 'in_progress'
+
+
+class StudentScoreCalculator:
+    """
+    Service dédié au calcul des scores des étudiants.
+    Single Responsibility: calculs de notes avec logique métier.
+    """
+    
+    def __init__(self, 
+                 grading_calculator: UnifiedGradingCalculator,
+                 db_provider: DatabaseProvider):
+        self.grading_calculator = grading_calculator
+        self.db_provider = db_provider
+    
+    def calculate_student_scores(self, assessment) -> Tuple[Dict[StudentId, StudentScore], Dict[ExerciseId, Dict[StudentId, float]]]:
+        """
+        Calcule les scores de tous les étudiants pour une évaluation.
+        Optimisé avec requête unique pour éviter N+1.
+        """
+        # Requête optimisée : toutes les notes en une fois
+        grades_data = self.db_provider.get_grades_for_assessment(assessment.id)
+        
+        # Organisation des données par étudiant et exercice
+        students_scores = {}
+        exercise_scores = defaultdict(lambda: defaultdict(float))
+        
+        # Calcul pour chaque étudiant
+        for student in assessment.class_group.students:
+            student_score = self._calculate_single_student_score(
+                student, assessment, grades_data
+            )
+            students_scores[student.id] = student_score
+            
+            # Mise à jour des scores par exercice
+            for exercise_id, exercise_data in student_score.exercises.items():
+                exercise_scores[exercise_id][student.id] = exercise_data['score']
+        
+        return students_scores, dict(exercise_scores)
+    
+    def _calculate_single_student_score(self, student, assessment, grades_data) -> StudentScore:
+        """Calcule le score d'un seul étudiant."""
+        total_score = 0
+        total_max_points = 0
+        student_exercises = {}
+        
+        # Filtrage des notes pour cet étudiant
+        student_grades = {
+            grade['grading_element_id']: grade 
+            for grade in grades_data 
+            if grade['student_id'] == student.id
+        }
+        
+        for exercise in assessment.exercises:
+            exercise_result = self._calculate_exercise_score(
+                exercise, student_grades
+            )
+            
+            student_exercises[exercise.id] = exercise_result
+            total_score += exercise_result['score']
+            total_max_points += exercise_result['max_points']
+        
+        return StudentScore(
+            student_id=student.id,
+            student_name=f"{student.first_name} {student.last_name}",
+            total_score=round(total_score, 2),
+            total_max_points=total_max_points,
+            exercises=student_exercises
+        )
+    
+    def _calculate_exercise_score(self, exercise, student_grades) -> Dict[str, Any]:
+        """Calcule le score pour un exercice spécifique."""
+        exercise_score = 0
+        exercise_max_points = 0
+        
+        for element in exercise.grading_elements:
+            grade_data = student_grades.get(element.id)
+            
+            if grade_data and grade_data['value'] and grade_data['value'] != '':
+                calculated_score = self.grading_calculator.calculate_score(
+                    grade_data['value'].strip(),
+                    element.grading_type,
+                    element.max_points
+                )
+                
+                if self.grading_calculator.is_counted_in_total(grade_data['value'].strip()):
+                    if calculated_score is not None:  # Pas dispensé
+                        exercise_score += calculated_score
+                    exercise_max_points += element.max_points
+        
+        return {
+            'score': exercise_score,
+            'max_points': exercise_max_points,
+            'title': exercise.title
+        }
+
+
+class AssessmentStatisticsService:
+    """
+    Service dédié aux calculs statistiques.
+    Single Responsibility: analyses statistiques des résultats.
+    """
+    
+    def __init__(self, score_calculator: StudentScoreCalculator):
+        self.score_calculator = score_calculator
+    
+    def get_assessment_statistics(self, assessment) -> StatisticsResult:
+        """Calcule les statistiques descriptives pour une évaluation."""
+        students_scores, _ = self.score_calculator.calculate_student_scores(assessment)
+        scores = [score.total_score for score in students_scores.values()]
+        
+        if not scores:
+            return StatisticsResult(
+                count=0,
+                mean=0,
+                median=0,
+                min=0,
+                max=0,
+                std_dev=0
+            )
+        
+        return StatisticsResult(
+            count=len(scores),
+            mean=round(statistics.mean(scores), 2),
+            median=round(statistics.median(scores), 2),
+            min=min(scores),
+            max=max(scores),
+            std_dev=round(statistics.stdev(scores) if len(scores) > 1 else 0, 2)
+        )
+
+
+# =================== FACADE pour simplifier l'utilisation ===================
+
+class AssessmentServicesFacade:
+    """
+    Facade qui regroupe tous les services pour faciliter l'utilisation.
+    Point d'entrée unique avec injection de dépendances.
+    """
+    
+    def __init__(self, 
+                 config_provider: ConfigProvider,
+                 db_provider: DatabaseProvider):
+        # Création des services avec injection de dépendances
+        self.grading_calculator = UnifiedGradingCalculator(config_provider)
+        self.progress_service = AssessmentProgressService(db_provider)
+        self.score_calculator = StudentScoreCalculator(self.grading_calculator, db_provider)
+        self.statistics_service = AssessmentStatisticsService(self.score_calculator)
+    
+    def get_grading_progress(self, assessment) -> ProgressResult:
+        """Point d'entrée pour la progression."""
+        return self.progress_service.calculate_grading_progress(assessment)
+    
+    def calculate_student_scores(self, assessment) -> Tuple[Dict[StudentId, StudentScore], Dict[ExerciseId, Dict[StudentId, float]]]:
+        """Point d'entrée pour les scores étudiants."""
+        return self.score_calculator.calculate_student_scores(assessment)
+    
+    def get_statistics(self, assessment) -> StatisticsResult:
+        """Point d'entrée pour les statistiques."""
+        return self.statistics_service.get_assessment_statistics(assessment)
\ No newline at end of file
diff --git a/tests/test_assessment_services.py b/tests/test_assessment_services.py
new file mode 100644
index 0000000..989ccba
--- /dev/null
+++ b/tests/test_assessment_services.py
@@ -0,0 +1,332 @@
+"""
+Tests pour les services d'évaluation refactorisés.
+
+Ce module teste la nouvelle architecture avec injection de dépendances
+et s'assure de la rétrocompatibilité avec l'API existante.
+"""
+import pytest
+from unittest.mock import Mock, MagicMock
+from dataclasses import asdict
+
+from services.assessment_services import (
+    AssessmentServicesFacade, 
+    AssessmentProgressService,
+    StudentScoreCalculator,
+    AssessmentStatisticsService,
+    UnifiedGradingCalculator,
+    GradingStrategyFactory,
+    NotesStrategy,
+    ScoreStrategy,
+    ProgressResult,
+    StudentScore,
+    StatisticsResult
+)
+from providers.concrete_providers import FlaskConfigProvider, SQLAlchemyDatabaseProvider
+
+
+class TestGradingStrategies:
+    """Test du pattern Strategy pour les types de notation."""
+    
+    def test_notes_strategy(self):
+        strategy = NotesStrategy()
+        
+        assert strategy.calculate_score('15.5', 20.0) == 15.5
+        assert strategy.calculate_score('0', 20.0) == 0.0
+        assert strategy.calculate_score('invalid', 20.0) == 0.0
+        assert strategy.get_grading_type() == 'notes'
+    
+    def test_score_strategy(self):
+        strategy = ScoreStrategy()
+        
+        assert strategy.calculate_score('0', 3.0) == 0.0
+        assert strategy.calculate_score('1', 3.0) == 1.0
+        assert strategy.calculate_score('2', 3.0) == 2.0
+        assert strategy.calculate_score('3', 3.0) == 3.0
+        assert strategy.calculate_score('4', 3.0) == 0.0  # Hors limites
+        assert strategy.calculate_score('invalid', 3.0) == 0.0
+        assert strategy.get_grading_type() == 'score'
+    
+    def test_strategy_factory(self):
+        notes_strategy = GradingStrategyFactory.create('notes')
+        score_strategy = GradingStrategyFactory.create('score')
+        
+        assert isinstance(notes_strategy, NotesStrategy)
+        assert isinstance(score_strategy, ScoreStrategy)
+        
+        with pytest.raises(ValueError, match="Type de notation non supporté"):
+            GradingStrategyFactory.create('invalid')
+    
+    def test_strategy_extensibility(self):
+        """Test que le factory peut être étendu avec de nouveaux types."""
+        class CustomStrategy:
+            def calculate_score(self, grade_value, max_points):
+                return 42.0
+            
+            def get_grading_type(self):
+                return 'custom'
+        
+        GradingStrategyFactory.register_strategy('custom', CustomStrategy)
+        custom_strategy = GradingStrategyFactory.create('custom')
+        
+        assert isinstance(custom_strategy, CustomStrategy)
+        assert custom_strategy.calculate_score('any', 10) == 42.0
+
+
+class TestUnifiedGradingCalculator:
+    """Test du calculateur unifié avec injection de dépendances."""
+    
+    def test_calculate_score_with_special_values(self):
+        # Mock du config provider
+        config_provider = Mock()
+        config_provider.is_special_value.return_value = True
+        config_provider.get_special_values.return_value = {
+            '.': {'value': 0, 'counts': True},
+            'd': {'value': None, 'counts': False}  # Dispensé
+        }
+        
+        calculator = UnifiedGradingCalculator(config_provider)
+        
+        # Test valeur spéciale "."
+        assert calculator.calculate_score('.', 'notes', 20.0) == 0.0
+        
+        # Test valeur spéciale "d" (dispensé)
+        assert calculator.calculate_score('d', 'notes', 20.0) is None
+        
+    def test_calculate_score_normal_values(self):
+        # Mock du config provider pour valeurs normales
+        config_provider = Mock()
+        config_provider.is_special_value.return_value = False
+        
+        calculator = UnifiedGradingCalculator(config_provider)
+        
+        # Test notes normales
+        assert calculator.calculate_score('15.5', 'notes', 20.0) == 15.5
+        
+        # Test scores normaux
+        assert calculator.calculate_score('2', 'score', 3.0) == 2.0
+    
+    def test_is_counted_in_total(self):
+        config_provider = Mock()
+        config_provider.is_special_value.return_value = True
+        config_provider.get_special_values.return_value = {
+            '.': {'counts': True},
+            'd': {'counts': False}
+        }
+        
+        calculator = UnifiedGradingCalculator(config_provider)
+        
+        assert calculator.is_counted_in_total('.') == True
+        assert calculator.is_counted_in_total('d') == False
+
+
+class TestAssessmentProgressService:
+    """Test du service de progression."""
+    
+    def test_calculate_grading_progress_no_students(self):
+        # Mock de l'assessment sans étudiants
+        assessment = Mock()
+        assessment.class_group.students = []
+        
+        db_provider = Mock()
+        service = AssessmentProgressService(db_provider)
+        
+        result = service.calculate_grading_progress(assessment)
+        
+        assert result.percentage == 0
+        assert result.status == 'no_students'
+        assert result.students_count == 0
+    
+    def test_calculate_grading_progress_normal(self):
+        # Mock de l'assessment avec étudiants
+        assessment = Mock()
+        assessment.id = 1
+        assessment.class_group.students = [Mock(), Mock()]  # 2 étudiants
+        
+        # Mock du provider de données
+        db_provider = Mock()
+        db_provider.get_grading_elements_with_students.return_value = [
+            {'completed_grades_count': 1},  # Élément 1: 1/2 complété
+            {'completed_grades_count': 2}   # Élément 2: 2/2 complété
+        ]
+        
+        service = AssessmentProgressService(db_provider)
+        result = service.calculate_grading_progress(assessment)
+        
+        # 3 notes complétées sur 4 possibles = 75%
+        assert result.percentage == 75
+        assert result.completed == 3
+        assert result.total == 4
+        assert result.status == 'in_progress'
+        assert result.students_count == 2
+
+
+class TestStudentScoreCalculator:
+    """Test du calculateur de scores étudiants."""
+    
+    def test_calculate_student_scores(self):
+        # Configuration des mocks
+        grading_calculator = Mock()
+        grading_calculator.calculate_score.return_value = 10.0
+        grading_calculator.is_counted_in_total.return_value = True
+        
+        db_provider = Mock()
+        db_provider.get_grades_for_assessment.return_value = [
+            {
+                'student_id': 1,
+                'grading_element_id': 1,
+                'value': '10',
+                'grading_type': 'notes',
+                'max_points': 20.0
+            }
+        ]
+        
+        # Mock de l'assessment
+        student = Mock()
+        student.id = 1
+        student.first_name = 'Jean'
+        student.last_name = 'Dupont'
+        
+        exercise = Mock()
+        exercise.id = 1
+        exercise.title = 'Exercice 1'
+        exercise.grading_elements = [Mock()]
+        exercise.grading_elements[0].id = 1
+        exercise.grading_elements[0].max_points = 20.0
+        exercise.grading_elements[0].grading_type = 'notes'
+        
+        assessment = Mock()
+        assessment.id = 1
+        assessment.class_group.students = [student]
+        assessment.exercises = [exercise]
+        
+        calculator = StudentScoreCalculator(grading_calculator, db_provider)
+        students_scores, exercise_scores = calculator.calculate_student_scores(assessment)
+        
+        assert len(students_scores) == 1
+        assert 1 in students_scores
+        
+        student_score = students_scores[1]
+        assert student_score.student_id == 1
+        assert student_score.student_name == 'Jean Dupont'
+        assert student_score.total_score == 10.0
+
+
+class TestAssessmentStatisticsService:
+    """Test du service de statistiques."""
+    
+    def test_get_assessment_statistics_no_scores(self):
+        score_calculator = Mock()
+        score_calculator.calculate_student_scores.return_value = ({}, {})
+        
+        service = AssessmentStatisticsService(score_calculator)
+        assessment = Mock()
+        
+        result = service.get_assessment_statistics(assessment)
+        
+        assert result.count == 0
+        assert result.mean == 0
+        assert result.median == 0
+    
+    def test_get_assessment_statistics_with_scores(self):
+        # Mock des scores étudiants
+        mock_scores = {
+            1: StudentScore(1, 'Student 1', 15.0, 20.0, {}),
+            2: StudentScore(2, 'Student 2', 18.0, 20.0, {}),
+            3: StudentScore(3, 'Student 3', 12.0, 20.0, {})
+        }
+        
+        score_calculator = Mock()
+        score_calculator.calculate_student_scores.return_value = (mock_scores, {})
+        
+        service = AssessmentStatisticsService(score_calculator)
+        assessment = Mock()
+        
+        result = service.get_assessment_statistics(assessment)
+        
+        assert result.count == 3
+        assert result.mean == 15.0  # (15+18+12)/3
+        assert result.median == 15.0
+        assert result.min == 12.0
+        assert result.max == 18.0
+
+
+class TestAssessmentServicesFacade:
+    """Test de la facade qui regroupe tous les services."""
+    
+    def test_facade_integration(self):
+        config_provider = Mock()
+        config_provider.is_special_value.return_value = False
+        
+        db_provider = Mock()
+        db_provider.get_grading_elements_with_students.return_value = []
+        db_provider.get_grades_for_assessment.return_value = []
+        
+        facade = AssessmentServicesFacade(config_provider, db_provider)
+        
+        # Vérifier que tous les services sont disponibles
+        assert hasattr(facade, 'grading_calculator')
+        assert hasattr(facade, 'progress_service')
+        assert hasattr(facade, 'score_calculator')
+        assert hasattr(facade, 'statistics_service')
+        
+        # Test des méthodes de la facade
+        assessment = Mock()
+        assessment.id = 1
+        assessment.class_group.students = []
+        
+        progress = facade.get_grading_progress(assessment)
+        assert isinstance(progress, ProgressResult)
+        
+        students, exercises = facade.calculate_student_scores(assessment)
+        assert isinstance(students, dict)
+        assert isinstance(exercises, dict)
+        
+        stats = facade.get_statistics(assessment)
+        assert isinstance(stats, StatisticsResult)
+
+
+class TestRegressionCompatibility:
+    """Tests de régression pour s'assurer de la rétrocompatibilité."""
+    
+    def test_grading_progress_api_compatibility(self):
+        """S'assurer que l'API grading_progress reste identique."""
+        config_provider = Mock()
+        db_provider = Mock()
+        db_provider.get_grading_elements_with_students.return_value = [
+            {'completed_grades_count': 5}
+        ]
+        
+        facade = AssessmentServicesFacade(config_provider, db_provider)
+        
+        assessment = Mock()
+        assessment.id = 1
+        assessment.class_group.students = [Mock(), Mock()]  # 2 étudiants
+        
+        progress = facade.get_grading_progress(assessment)
+        
+        # L'API originale retournait un dict, vérifions les clés
+        expected_keys = {'percentage', 'completed', 'total', 'status', 'students_count'}
+        actual_dict = asdict(progress)
+        
+        assert set(actual_dict.keys()) == expected_keys
+    
+    def test_calculate_student_scores_api_compatibility(self):
+        """S'assurer que calculate_student_scores garde la même signature."""
+        config_provider = Mock()
+        config_provider.is_special_value.return_value = False
+        
+        db_provider = Mock()
+        db_provider.get_grades_for_assessment.return_value = []
+        
+        facade = AssessmentServicesFacade(config_provider, db_provider)
+        
+        assessment = Mock()
+        assessment.id = 1
+        assessment.class_group.students = []
+        assessment.exercises = []
+        
+        students_scores, exercise_scores = facade.calculate_student_scores(assessment)
+        
+        # L'API originale retournait un tuple de 2 dicts
+        assert isinstance(students_scores, dict)
+        assert isinstance(exercise_scores, dict)
\ No newline at end of file