diff --git a/lib/core/services/auth_service.dart b/lib/core/services/auth_service.dart
index 0eb78a5..4ad822a 100644
--- a/lib/core/services/auth_service.dart
+++ b/lib/core/services/auth_service.dart
@@ -90,6 +90,20 @@ class AuthService {
     }
   }
 
+  /// Ler schoolClassId do aluno na Firestore (turma escolar definida no registo)
+  static Future<String?> getStudentSchoolClassId(String uid) async {
+    try {
+      final doc = await _firestore.collection('users').doc(uid).get();
+      if (doc.exists) {
+        return doc.data()?['schoolClassId'] as String?;
+      }
+      return null;
+    } catch (e) {
+      print('DEBUG: Erro ao ler schoolClassId: $e');
+      return null;
+    }
+  }
+
   /// Ler role do usuário na Firestore
   static Future<String?> getUserRole(String uid) async {
     try {
diff --git a/lib/features/classes/presentation/pages/join_class_page.dart b/lib/features/classes/presentation/pages/join_class_page.dart
index a664162..2180e5a 100644
--- a/lib/features/classes/presentation/pages/join_class_page.dart
+++ b/lib/features/classes/presentation/pages/join_class_page.dart
@@ -47,8 +47,8 @@ class _JoinClassPageState extends State<JoinClassPage> {
         return;
       }
 
-      // Ler classId autorizado do aluno (definido no registo)
-      final authorizedClassId = await AuthService.getStudentClassId(
+      // Ler schoolClassId autorizado do aluno (definido no registo)
+      final studentSchoolClassId = await AuthService.getStudentSchoolClassId(
         currentUser.uid,
       );
 
@@ -67,9 +67,14 @@ class _JoinClassPageState extends State<JoinClassPage> {
 
       final classDoc = classQuery.docs.first;
       final classId = classDoc.id;
+      final classSchoolClassId =
+          classDoc.data()['schoolClassId'] as String?;
 
       // Verificar se o aluno está autorizado a entrar nesta turma
-      if (authorizedClassId == null || authorizedClassId != classId) {
+      // O schoolClassId do aluno deve corresponder ao schoolClassId da disciplina
+      if (studentSchoolClassId == null ||
+          classSchoolClassId == null ||
+          studentSchoolClassId != classSchoolClassId) {
         setState(() => _isLoading = false);
         _showError(
           'Não tens permissão para entrar nesta turma.\n'