Everyone's forever telling you what to do in school. Your parents tell you to attend, the school staff members tell you what to write, what to eat, what to wear, who to go out with (and who not to)... the list goes on and on. It's a lot like prison, apart from the fact that you did nothing wrong. You would guess that after pressuring you to attend class and all these things, they'd at the very least be decent enough allow you to visit whichever sites you will want to when you are there. Well, no. The internets are censored, a great deal of sites are blocked. Fortunately, there are a couple of ways to unblock websites, and it's a good deal more easy than convincing your parents to homeschool you.
Unblockers are like a gateway that sit between the computer you're on and the site you want to go to. The unblocker accesses the site you want on your behalf, loads the page, and forwards it to you. So the site you're trying to visit never sees your IP. So in effect you are surfing websites in an indirect way. School firewalls think you are just visiting the unblocker, not the real site.
An alternative method of unblocking Facebook in school is by making your own unblocker site. This is harder than using someone else's unblocker but it pays off because you can make more of them. How to do this is not in this guide, but if you search for "How to make your own proxy" you should find help. You can even earn money from this through advertising.
Other ways to access Facebook are by using sites that translate pages, like Google Translate or Babelfish. Also try Google's cached version of the site. However, you can't to log in that way, so it's still better to use unblockers for Facebook, however these tricks are good for most other sites.