Dear Karl-Henrik,
Thank you for reaching out. There is no need to remove and re-add the students. You can manage their permissions using the following steps:
1. Open OneNote Online(OneNote | Microsoft 365 Copilot) and locate the Class Notebook.
2. Click to open the file location.
3. Create a new folder at this location and name it "test."
4. Copy the notebook name.
5. Open the "test" folder, find "test" at the end of the URL bar, and replace it with the notebook name you copied. Press Enter to access the partition under the notebook.
6. Locate the Students sections and click Manage Access to review user permissions. Remove any unnecessary permissions for the affected students.
After making these changes, please check if the issue is resolved. Let us know if you need any further assistance.
Best regards,
Community Moderator | Sophia