At school, everyone always wants to tell you what to do. Parents tell you to attend, your school staff members tell you what to write, what to eat, what to wear, who to spend time with (and who not to)... the list goes on and on. It's a lot like prison, apart from the fact that you didn't commit a crime. You'd think that after forcing you to go there and all that stuff, they would at least be decent enough let you browse whichever websites you would need while you're stuck there. Apparently not. The internets are censored, and lots sites are blocked. Luckily, there are a few ways to unblock web sites at least, and it's very much easier than convincing your parents to unschool you.
An unblocker is like a gateway that sit between your computer and the site you're trying to visit. The unblocker goes to the site you want instead of you, downloads the page, and sends it off to you. So the site you want to be on never sees your IP. So actually you are browsing sites in an indirect manner. Internet filters think you are just accessing the unblocker, not the destination site.
Another way of unblocking Facebook in school is to make your own unblocker tool. This is more advanced than using someone else's unblocker but it pays off because you're in control. Explaining 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 also make some money from letting people use it if you put ads on it.
Other ways to get on Facebook are by using sites that translate pages, for example Google Translate or Babelfish. You can also try using Google's cache copy of the site. Although, you can't to log in using these methods, so you're better off using unblockers for Facebook, however these tricks are great for most websites.