Try Groovix. This was mentioned above, but it's been overwhelmed by do-it-yourself solutions, and if you're the one IT guy for a charter school, you probably need it simple and reliable. Check out their distro. It's based on Ubuntu, and you can download it from their web site.
For more info, check this page: http://groovix.com/slim.html
which explains how they support up to 10 seats (monitor, keyboard, mouse and speakers) per computer.
There's an article about Groovix being used in Maryland libraries here: http://www.linux.com/article.pl?sid=06/09/22/15422 54