It depends on how your school has their network set up. If they have a proxy server that scans a list of acceptable sites and rejects all others, Facebook would have to be on that list to connect. If it isn't, there's nothing you can do on your local machine to change it.
If the school is blocking specific sites and allowing all others, connecting to an accepted proxy server might get you there. If you want to try, enter "Facebook" in the search box at the top right and you will see some of the proxy inks there.
Answered Jan 24, 2012
Edited Jan 24, 2012