diff --git a/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/Classroom.java b/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/Classroom.java
--- a/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/Classroom.java
+++ b/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/Classroom.java
@@ -19,8 +19,8 @@ private URL gitlabUrl;
 
     private Long gitlabGroupId;
 
-    @ManyToOne
-    private ClassroomUser teacher;
+    @ManyToMany(fetch = FetchType.EAGER)
+    private Set<ClassroomUser> teachers = new HashSet<>();
 
     @ManyToMany(fetch = FetchType.EAGER)
     private Set<ClassroomUser> students = new HashSet<>();
@@ -52,12 +52,16 @@ public void setGitlabUrl(URL gitlabUrl) {
         this.gitlabUrl = gitlabUrl;
     }
 
-    public ClassroomUser getTeacher() {
-        return teacher;
+    public Set<ClassroomUser> getTeachers() {
+        return teachers;
     }
 
-    public void setTeacher(ClassroomUser teacher) {
-        this.teacher = teacher;
+    public void setTeachers(Set<ClassroomUser> teachers) {
+        this.teachers = teachers;
+    }
+
+    public void addTeacher(ClassroomUser teacher) {
+        this.teachers.add(teacher);
     }
 
     public Set<ClassroomUser> getStudents() {
diff --git a/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImpl.java b/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImpl.java
--- a/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImpl.java
+++ b/src/main/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImpl.java
@@ -50,7 +50,7 @@ @Override
     public void createClassroom(String classroomName, Long parentGitlabGroupId, ClassroomUser teacher) throws GitLabApiException {
         var classroom = new Classroom();
         classroom.setName(classroomName);
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
 
         this.gitlab.createGroup(classroom, Optional.ofNullable(parentGitlabGroupId));
 
diff --git a/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImpl.java b/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImpl.java
--- a/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImpl.java
+++ b/src/main/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImpl.java
@@ -88,9 +88,14 @@
     @Override
     public Project createStudentProject(ExerciseAssignment exerciseAssignment, ClassroomUser student) throws GitLabException {
         var classroom = exerciseAssignment.getClassroom();
-        var teacher = classroom.getTeacher();
-        // get a gitlab api client ith the teacher's rights
-        var teacherGitlabApi = this.gitlabApiFactory.userGitlabApi(teacher);
+
+        var teacher = classroom.getTeachers().stream().findFirst();
+
+        if(teacher.isEmpty()){
+            throw new GitLabException("Could not create student %s project for assignment %s. Classroom has no teacher.".formatted(student.getName(), exerciseAssignment.getName()));
+        }
+        // get a gitlab api client with the teacher's rights
+        var teacherGitlabApi = this.gitlabApiFactory.userGitlabApi(teacher.get());
 
         // create the project if needed
         var project = this.ensureStudentProjectExists(teacherGitlabApi, exerciseAssignment, student);
diff --git a/src/main/resources/db/migration/V20__CLASSROOM_TEACHERS.sql b/src/main/resources/db/migration/V20__CLASSROOM_TEACHERS.sql
new file mode 100644
--- /dev/null
+++ b/src/main/resources/db/migration/V20__CLASSROOM_TEACHERS.sql
@@ -0,0 +1,22 @@
+CREATE TABLE classroom_teachers
+(
+    classroom_id  UUID         NOT NULL,
+    teachers_name VARCHAR(255) NOT NULL,
+    CONSTRAINT pk_classroom_teachers PRIMARY KEY (classroom_id, teachers_name)
+);
+
+ALTER TABLE classroom_teachers
+    ADD CONSTRAINT fk_classroom FOREIGN KEY (classroom_id) REFERENCES classroom (id);
+
+ALTER TABLE classroom_teachers
+    ADD CONSTRAINT fk_classroom_user FOREIGN KEY (teachers_name) REFERENCES classroom_user (name);
+
+-- migrate data to new table
+INSERT INTO classroom_teachers (classroom_id, teachers_name)
+    SELECT id, teacher_name FROM classroom;
+
+ALTER TABLE classroom
+    DROP CONSTRAINT fk_classroom_user;
+
+ALTER TABLE classroom
+    DROP COLUMN teacher_name;
diff --git a/src/test/java/fr/univ_lille/gitlab/classrooms/assignments/AssignmentServiceImplTest.java b/src/test/java/fr/univ_lille/gitlab/classrooms/assignments/AssignmentServiceImplTest.java
--- a/src/test/java/fr/univ_lille/gitlab/classrooms/assignments/AssignmentServiceImplTest.java
+++ b/src/test/java/fr/univ_lille/gitlab/classrooms/assignments/AssignmentServiceImplTest.java
@@ -81,7 +81,7 @@ void acceptExerciceAssignment_shouldCreateAGitlabProject() throws GitLabApiException, GitLabException {
         var teacher = new ClassroomUser();
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
 
         var assignment = new ExerciseAssignment();
         assignment.setName("Exercice 1");
@@ -116,7 +116,7 @@ void acceptAssignment_shouldUpdateGitlabInfo_ifExerciseAssignmentIsAlreadyAccepted() throws GitLabApiException, GitLabException {
         var teacher = new ClassroomUser();
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
 
         var assignment = new ExerciseAssignment();
         assignment.setName("Exercice 1");
diff --git a/src/test/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImplTest.java b/src/test/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImplTest.java
--- a/src/test/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImplTest.java
+++ b/src/test/java/fr/univ_lille/gitlab/classrooms/classrooms/ClassroomServiceImplTest.java
@@ -76,6 +76,8 @@ verify(classroomRepository).save(classroomCaptor.capture());
 
         assertThat(classroomCaptor.getValue())
                 .isNotNull()
-                .hasFieldOrPropertyWithValue("teacher.name", "obiwan.kenobi");
+                .satisfies(it -> {
+                    assertThat(it.getTeachers()).contains(teacher);
+                });
     }
 }
diff --git a/src/test/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImplTest.java b/src/test/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImplTest.java
--- a/src/test/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImplTest.java
+++ b/src/test/java/fr/univ_lille/gitlab/classrooms/gitlab/GitlabImplTest.java
@@ -129,7 +129,7 @@ group.setFullPath("my-group/path");
         when(gitLabApi.getGroupApi().getOptionalGroup(72L)).thenReturn(Optional.of(group));
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
         classroom.addAssignment(assignment);
 
         when(gitlabApiFactory.userGitlabApi(teacher)).thenReturn(gitLabApi);
@@ -160,6 +160,30 @@ verifyNoMoreInteractions(gitLabApi.getProjectApi());
     }
 
     @Test
+    void createProject_shouldNotCreateAProject_ifClassroomHasNoTeacher() throws GitLabApiException, GitLabException {
+        var student = new ClassroomUser("luke.skywalker", List.of(ClassroomRole.STUDENT));
+        student.setGitlabUserId(8L);
+
+        var assignment = new ExerciseAssignment();
+        assignment.setName("Exercice 1");
+        assignment.setGitlabGroupId(72L);
+
+        var group = new Group();
+        group.setId(72L);
+        group.setFullPath("my-group/path");
+        when(gitLabApi.getGroupApi().getOptionalGroup(72L)).thenReturn(Optional.of(group));
+
+        var classroom = new Classroom();
+        classroom.addAssignment(assignment);
+
+        assertThatThrownBy(() -> gitlab.createStudentProject(assignment, student))
+                .isInstanceOf(GitLabException.class)
+                .hasMessage("Could not create student luke.skywalker project for assignment Exercice 1. Classroom has no teacher.");
+
+        verifyNoMoreInteractions(gitLabApi.getProjectApi());
+    }
+
+    @Test
     void createProject_shouldNotCreateAProject_ifProjectAlreadyExists() throws GitLabApiException, GitLabException {
         var student = new ClassroomUser("luke.skywalker", List.of(ClassroomRole.STUDENT));
         student.setGitlabUserId(8L);
@@ -175,7 +199,7 @@ group.setFullPath("my-group/path");
         when(gitLabApi.getGroupApi().getOptionalGroup(72L)).thenReturn(Optional.of(group));
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
         classroom.addAssignment(assignment);
 
         when(gitlabApiFactory.userGitlabApi(teacher)).thenReturn(gitLabApi);
@@ -211,7 +235,7 @@ group.setFullPath("my-group/path");
         when(gitLabApi.getGroupApi().getOptionalGroup(72L)).thenReturn(Optional.of(group));
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
         classroom.addAssignment(assignment);
 
         when(gitlabApiFactory.userGitlabApi(teacher)).thenReturn(gitLabApi);
@@ -246,7 +270,7 @@ group.setFullPath("my-group/path");
         when(gitLabApi.getGroupApi().getOptionalGroup(72L)).thenReturn(Optional.of(group));
 
         var classroom = new Classroom();
-        classroom.setTeacher(teacher);
+        classroom.addTeacher(teacher);
         classroom.addAssignment(assignment);
 
         when(gitlabApiFactory.userGitlabApi(teacher)).thenReturn(gitLabApi);