Ne réinvente pas la roue

users/forms.py

@@ -454,23 +454,15 @@ class GroupForm(FormRevMixin, ModelForm):
         widget=forms.CheckboxSelectMultiple,
         required=False
     )
-    superuser = forms.BooleanField(
-        label="Superuser",
-        required=False,
-    )
 
     class Meta:
         model = User
-        fields = ['groups']
+        fields = ['groups', 'is_superuser']
 
     def __init__(self, *args, **kwargs):
         prefix = kwargs.pop('prefix', self.Meta.model.__name__)
         super(GroupForm, self).__init__(*args, prefix=prefix, **kwargs)
-        self.fields['superuser'].initial = self.instance.is_superuser
-
-    def save(self, *args, **kwargs):
-        self.instance.is_superuser = self.cleaned_data['superuser']
-        return super(GroupForm, self).save(*args, **kwargs)
+        self.fields['is_superuser'].label = "Superuser"
 
 
 class SchoolForm(FormRevMixin, ModelForm):