From what I remember (from way back in high school) the local Board of Education licensees out web-filtering software to help block sites.
The company that makes the software (in my case it was Websense) complies a list of all the sites they can and categories them.
Then someone at the BoE (probably the Superintendent) orders certain categories to be blocked (Porn, Video Games, Extremest, P2P, etc.). So when they blocked Game sites (probably to prevent people from playing flash and shockwave type games) they also blocked sites that just give information about video-games (gamespot.com, wcnews.com, ign.com, etc.)
They can whitelist sites, but they usualy don't listen to students and its nearly impossible to get a teacher or administration to put in a request for a game site.
However, you can set up a proxy using your home computer. Just go to
http://peacefire.org/ to find out how (it can even bypass China's firewall, so I doubt you're local town's BoE would pose a challenge).