If it was me, and I had only one (nice) bike to ride to school, I would get a really good chain with a really good padlock, and also cable up any separable parts like the seat and so on.

Or you might consider taking the seat off and carrying it with you.

I have often wondered if certain clipless pedals might deter a theif, something that would not work with regular shoes very well like Crank Bros. Eggbeaters. Or maybe that would make the bike a more attractive target, I'm not sure.