If you see any student accounts listed as teachers in the Admin Dashboard then these students will have accidentally signed in as a teacher. You will want to adjust these accounts to remove teacher only features from the students (such as control over book sharing) and to ensure compliance with all applicable privacy laws.
From the Teachers panel, use the picker to choose the email accounts affected.
Click the Bulk Actions dropdown and choose Switch to student
The account will be removed from the organisation list, and these students will now need to sign in as a student the next time they try to sign in.