Everyone's constantly telling you what to do while in school. Parents tell you to go, the teachers tell you what to learn, what to eat, what to wear, who to go out with (and who not to)... the list goes on and on. You'd swear you're in jail. You would think that since you're forced to go to and all these things, they would at the very least have the decency to permit you to browse whichever web sites you need to as long as you are visiting there. Apparently not. The interwebs are censored, many web sites are blocked. As luck would have it, there are a couple of ways to get past the internet filter, and it's a lot more easy than convincing your parents to unschool you.
An unblocker is a kind of gateway that pass information between the computer you're on and the site you want to go to. The unblocker accesses the site on your behalf, accesses the page, and sends it on to you. So the site you're trying to visit never sees your IP. So actually you are browsing sites indirectly. School firewalls only see you visiting the unblocker, not the destination site.
Another way to unblock Facebook at school is to set up your own unblocker site. This is harder than just using an unblocker but better in the long run because you can make more of them. Explaining how to do this is not in this guide, if you do a search for "How to make your own proxy" you will find info. You can also earn money from letting people use it through advertising.
Some other ways to unblock Facebook include to use translator sites, for example Google Translate or Babelfish. You can also try using Google's cache version of the site. Unfortunately, you can't to log in using these methods, so it's still best to use unblockers for Facebook, though these tips work with most websites.