Everyone's always bossing you around while at school. Parents tell you to go, your school staff tell you what to think, what to eat, what to wear, who to go out with... the list goes on and on. It's a lot like you are being treated like a felon or something like that. You would expect that since you are pressured to go there and all that stuff, they would at least let you browse whichever websites you will like when you are held captive there. Apparently not. The internets are censored, many websites are being blocked. Fortunately, there are a couple of ways of bypassing the restrictions, and it's very much more easy than convincing your parents to homeschool you.
Unblockers are like a gateway that work between the computer you're on and the site you're trying to visit. The unblocker goes to the site you want on your behalf, downloads the page, and sends it on to you. So the site you're trying to visit only sees the unblocker's IP. So, basically you are browsing sites in an indirect way. School filters think you are just accessing the unblocker, not the real site.
Another method to unblock Facebook at school is by setting up your own unblocker site. This is more advanced than using an unblocker but it's a lot nicer to have because if they block it, you can make another. How to do this is not in this guide, if you search for "How to make your own proxy" you will find info. You can also make some money from letting people use it through advertising.
Other ways to get on Facebook include by using sites that translate pages, such as Google Translate or Babelfish. You can also try using Google's cache copy of the site. However, it won't let you to log in that way, so it's still better to use unblockers for Facebook, however these tricks work well for many other sites.