At school, you're constantly being told what to do. Parents and teachers are telling you what you should write, which friends you should hang out with, what you ought to wear, and even what you must eat. It's a long list. You'd swear you're behind bars or something like that. You'd guess that since you're being coerced to go there and all that stuff, they'd at least let you browse whatever sites you want as long as you're visiting there. Alas, that is not the case. The internet is censored, and many web sites are blocked. Even so, there are a few ways to go past that at least, and it's a lot more easy than convincing your parents to homeschool you.
Unblockers are like a gateway that work between your computer and the site you're visiting. The unblocker goes to the site you want in your place, downloads the page, and sends it on to you. So the site you want to access only sees the unblocker's IP. So in effect you are visiting websites in an indirect manner. Internet filters only see you accessing the unblocker, not the real site.
An alternative way to unblock Facebook in school is by setting up your own unblocker site. This is more complicated than using an unblocker but better in the long run because if they block it, you can make another. How to do this is beyond the scope of this article, if you do a search for "How to make your own proxy" you will find info. You can even make money from your unblocker if you put ads on it.
Other ways to access Facebook are to use translator sites, like Google Translate or Babelfish. Also try Google's cached version of the site. However, it's not possible to login using these methods, so it's still best to use unblockers for Facebook, however these tricks are good with most other sites.