Set up a proxy on your home computer. That's what I'm working on right now. I'm using a linux based proxy (squid), but you might be able to find some that run on Windows. Since usually my ip changes when I turn my router on and off, it can be dynamic every day. If you need to though you also could find some IP changing software.
If you do make your own proxy, let a friend test it so they'll bite the bullet if the school gets mad. That's what I'll do. I have a communist friend who wants to go to a bunch of blocked sites. If he gets caught and kicked from school computers I know not to try it.
UPDATE: Firewall and Router working I'm planning on setting up my proxy tomorrow after school.