If you experience issues where a student have access to see another student's Class Notebook, they may have a permissions issue. This can happen as a result of repeated of group membership from within Microsoft Team.
When you change a student from a member to an owner, they gain full access to all notebook sections. Attempting to change the student back to a member will create new student section, if it doesn’t exist to the user. It also gives them access to Collaboration Space and Content Library and their own student sections.
Because Class Notebooks inherit permission from the Microsoft Teams, it is not recommended to change the membership of the students in the Team.
Note: if you need to transfer ownership of a Class Notebook , please follow the procedure listed here.