My school banned cell phones too......being a private school they did allow you to pay a fee of I believe $200 for the right to keep your cell phone turned off in your locker.

For some STRANGE reason, no matter how hot it was outside I would always wear my jacket, with the cell phone in the "secret pocket" always on vibrate. If I got a call, I'd ask to go to the bathroom and see what was going on, never got caught