Students should not be able to add or remove files in the Files Tab. Or let me add a view only OneDrive tab.
The files tab should be for the class content provided by the teacher. It should not collect all the attachments or pictures the students upload to the conversations tab. Also, it should not let student remover any file.
Or else let us add a onedrive tab for us to share files for the students.
Only 2 votes?! I agree, a permission level somewhat between guests and members is needed e. g. excluding the ability to delete files (or, trmas obviously not mirroring SharePoint permissions) just hide the delete file)! Malicious students might take advantage of this option once they've figured out they can ...