How to lock up a Skateboard?

I want to skate to school but my teachers aren't cool with me taking it in classes and on campus. So i need to lock it up or let my principal take it, which i dont want to give to him. So how would/could i lock up my board in the bikesheds without modifying my board in any way? Will a bike lock do it? Preferably answers from people who have experianced this probkem. Thanks!