our school uses bess too... you can use a really easy method that me and one of my friends used. though i did hear that it was traceable, nobody ever said anything to me about it, so i don't know if it is fully true. all you have to do is go to
http://www.metacrawler.de and search for the address of the website you want to go to. then click the link under the page description that says Öffne Anonym... which in english means Open Anonymously. it goes through metacrawler's metaproxy to access websites. have fun, but be careful... most school network admins are spaztacular.... or at least the ones around my area.