a good start (Score 1)

One thing you can do to deter the downloading that is extremely simple in xp pro is to log into the admin account delete all users then go into my computer and right click on your hard drive go to properties then to the quota tab and enable quota management and limit disk space to for kids in high school i would say no more than 10 to 50 megs of space enough for then to store documents and such then i am guessing this is a lab used during class - create limited user names with passwords on the machine and assign seats to the students so they all get their little section of the hard drive this will effectivly limit them to how much they could possibly download and store on the machine no more game downloads or music downloads as they won't have space and the machine won't let them exceed that space. Like i said this won't change them from making changes to the settings but will prevent them abusing the school's net connection.