These things don't belong at school in the first place. Perhaps your teachers are taking them. (If they aren't, they should be.)
If you must spend your time being lazy instead of learning, and prefer a life of gas pumping to one of luxury, then by all means listen to your music and play your games and watch your videos. Hey, somebody needs to make my hamburger and fries. If that's what you prefer, then I'd say that you should have them in your hands or pockets at all times. If somebody is stealing them and you don't know who, then you are obviously putting them down. Don't do that. The fact that you would do that and not be able to understand how people manage to steal them is one symptom of not learning anything - you are melting your brain instead of exercising it.
You only get one brain - I think you might want to start using it instead of letting it just sit there growing mold.