How broadly do you propose to enforce such a ban? Most students do their homework at home so I'm not sure how you're imagining this would work. Even for exams

How broadly do you propose to enforce such a ban? Most students do their homework at home so I'm not sure how you're imagining this would work. Even for exams I had my cellphone and backpack on me. You just weren't allowed into them. The only exception to that in my experience was exams proctored in a dedicated testing center where there are lockers, multiple human observers, and lots of cameras.