If we stored our stuff on school grounds we could only access it (easily) on school days after classes end, which isn't too much of an issue since even the Reflective Detectives need a break some times. Sho's also right, but we could also pack our weapons in with a bunch of boxes and other stuff. But I dunno. It'd be hard getting some of the weapons some of us use into anywhere, but at least at school we have clubs which could excuse the fact that we're carrying some weapons. (Such as archery, kendo, etc)