diff --git a/app/api/partitions.py b/app/api/partitions.py
index 699f18e7..0b297871 100644
--- a/app/api/partitions.py
+++ b/app/api/partitions.py
@@ -19,6 +19,7 @@ from app.models import FormSemestre, FormSemestreInscription, Identite
 from app.models import GroupDescr, Partition
 from app.models.groups import group_membership
 from app.scodoc import sco_cache
+from app.scodoc import sco_groups
 from app.scodoc.sco_permissions import Permission
 from app.scodoc import sco_utils as scu
 
@@ -172,22 +173,11 @@ def set_etud_group(etudid: int, group_id: int):
     group = query.first_or_404()
     if etud.id not in {e.id for e in group.partition.formsemestre.etuds}:
         return json_error(404, "etud non inscrit au formsemestre du groupe")
-    groups = (
-        GroupDescr.query.filter_by(partition_id=group.partition.id)
-        .join(group_membership)
-        .filter_by(etudid=etudid)
+
+    sco_groups.change_etud_group_in_partition(
+        etudid, group_id, group.partition.to_dict()
     )
-    ok = False
-    for other_group in groups:
-        if other_group.id == group_id:
-            ok = True
-        else:
-            other_group.etuds.remove(etud)
-    if not ok:
-        group.etuds.append(etud)
-        log(f"set_etud_group({etud}, {group})")
-    db.session.commit()
-    sco_cache.invalidate_formsemestre(group.partition.formsemestre_id)
+
     return jsonify({"group_id": group_id, "etudid": etudid})
 
 
diff --git a/app/models/groups.py b/app/models/groups.py
index 4fd25a94..6fafa234 100644
--- a/app/models/groups.py
+++ b/app/models/groups.py
@@ -87,6 +87,7 @@ class Partition(db.Model):
     def to_dict(self, with_groups=False) -> dict:
         """as a dict, with or without groups"""
         d = dict(self.__dict__)
+        d["partition_id"] = self.id
         d.pop("_sa_instance_state", None)
         d.pop("formsemestre", None)