Sometimes just to hassle bikers I hop out of my Hummer and place extra locks on a few bikes, then drive off leaking oil. Seriously that would likely really bug me. I'd try to pick the lock, (if it was a round type using a bic pen). Master locks, (mirror keyed) can be easy to pick with a special filed off key. Some locks you can break by hand. I'd love to be able to remove my bike and leave the other unlocked.

Of course how much of this problem is that the city or school has inadequate bike racks?