Call up the profile of the person concerned via the user administration. You can find this in the drop-down menu in the header at the top right. Then find the person using the search bar.
Tap on the tile to open the profile.
NOTE: You can only save the teacher as a class teacher or co-class teacher if this person has saved an abbreviation in Sdui. See the linked FAQ article "How do I change the abbreviation for teachers".
Scroll down to the bottom of your profile.
Here you can enter the setting as a class teacher or co-class teacher.
NOTE: There can only be one class teacher in Sdui, but there can be more than one co-class teacher.
Based on this assignment, the teacher is automatically synchronized in the corresponding class and parent group.