Cell phones in shoe organizer with student numbers. They are at the front of the classroom so all have clear view of their phone and can't say that someone "messed" with their phone. They are numbered to indicate which phone belongs to which student.
I made this for my high school Culinary Arts classroom. Works like a CHARM! After first few days of school and students getting used to rules, have never had a problem! -Chef lock them on the inside of the closet of its avilable