If you could access its database, you could probably create a page that feeds the address in and see if its hits anyone in its database and returns a message based on that.
I know of ClickView which is designed for education sector and handles Videos in what appears to be the same way, or you could whip something up with phpmotion and if you wanted to do it from within a browser for free.
There are users of both solutions on the forums around here, and i'm sure theres other methods, those are just what jumped into my head.
I know some classroom monitoring packages (eg: Lanschool/ABTutor) have functions where the students can chat to the teacher, Have you thought about trying these?
Dell can load preconfigured images onto systems if you want, but i think you may need a larger order for them to do it. But creating a image and sending it out to all the systems shouldn't take all that long, how are you setting them up?
Depending on what you want, They are pretty lacking in features (even more than the vanilla forum package), not to say that it is automatically a bad thing.
I know that a couple of people on here ended up updating the xp firmware on the MagicInfo screens so they could end up running Xibo compared to the MI stuff, Try having a read of that big Xibo thread that is around here somewhere.
MediaWiki can do kinda that, it does versioning on edits (EG: Revision history of "About EduGeek.net" - Wiki). But it sounds you more want a VCS as dhicks pointed out, such as Git, SVN, RCS to point out a few.
"You didn't have to slam the door behind you"
Not only do you confuse them with the missing door, they start thinking you are hearing things in your head.
I would setup a "public" wifi for them to use and just filter it with your own proxy.
Just because you don't need a proxy inbetween your connection anymore doesn't you can't have it and use that for authentication.
ATM the most played on my media players would be:
* Tim Berg - Bromance (Avicii's Arena Mix)
* Armin Van Buuren feat. Sophie Ellis-Bextor - Not Giving Up On Love (Jorn Van Deynhoven Remix)
Does it say it must be printed once completed? could you not wait till the end them print them all in one batch when they are near perfect (and could also do it in duplex to save paper)?