Teachers are team owners and can remove co-teachers from a class team. Removing a co-teacher removes their owner permissions in the team.
Remove a co-teacher
Navigate to the class team you’d like to edit, then select the More options next to the class name.
Select Manage team.
Navigate to the co-teacher you're removing and change their role from Owner to Member by selecting the downward arrow.
Now, select the X at the end of the co-teacher's row. The co-teacher will be removed from your class.