Okay, try to get the program a4proxy and install it on the school computer. It has thousands of proxies you can use directly, and there is no way the school has blocked all of them.
You will have to pay for it though if you want it, but I think it's cheap. You might also try to see if there is a crack for the program. The trial doesn't come with all the proxies ...
I would give you the program directly but I am not sure where I have put the full version of the program.