If your school has implemented the change of school year in Sdui , the first step would be for all class teachers to determine their class(es) again.
To do this, go to your profile and enter your class(es) under "Class teacher of" or "Co-class teacher of".
This step will assign you to the class groups created for the new school year.
You can find these by clicking on "Chats" in the footer of the app and then scrolling down the list.
Under "not yet active" you will find your new class group(s).
To activate it, just send a message in the chat. This moves the chat up the list.