One of my students does this, too. It happened when it seemed as if the student control on the gray camera box area was suddenly not there anymore. It must have been a glitch that day.

I just checked with my own iPad and if I have my pdfs and images locked, the student can't (shouldn't be able to) delete them. I understand we have to unlock things, though, and we want them to be able to collaborate and use the tools.

What my student has done after I have turned off her control...is .. she has left or refreshed the classroom. When I allow her back in, she sometimes deletes before I can turn her control off again. Is this what is happening to you?

Is there a way to keep the student's control turned off if they leave or refresh--until the teacher is ready to give back control, Noah Kaufman?