Electrifying my backpack how to do it and if it's not good?

OK, so kids at school are bugging me by getting into my backpack. Could I charge a capacitor to electrify the zipper so it gives them a nasty little shock? Could I do this? How much would it cost? Would it be easy, my dad's an electrician by trade so he should be able to help. Could I get in trouble at school? And please, I don't care about the bullying and what not, just a sort of useful science experiment. Thanks Mason