Well - I'm so glad to say that our school is finally looking at whitelist filtering!
I've set up a new proxy (using Jana Server within Windows) that points to a txt file full of allowed sites. I have also designed a web app that uses ldap to allow staff only to add websites to the txt file to allow sites. It also adds an entry to a mySQL db that populates a student home page of sites they are allowed so they know what they can access.
We're gonna start implementing it with certain students - rather than banning the naughty ones we're gonna put them onto the whitelist filtering instead meaning they can access certain sites but can't muck about.
How do others manage their whitelist filtering? How do staff open up sites? Do they have to ask you or can they do it themselves?