I can fix those kids for ya. :-)
The easiest way is to add a custom registry key for that purpose. Since my two sisters are teachers who had a similar issue (in fact, one is in Dayton and the other in Cincinnati, imagine that), I have created a registry file that will easily perform the update. Plus I have a second one that will reverse the action as well.
With it installed, they won't be able to change any Desktop settings.
I'd make one that slapped their hands, too, but I haven't figured out how to do that yet. :D
Anyway, I will be happy to send you the two REG files in a zip file as an attachment if you send me an email. Just go to my profile page in TR and click on 'Send Private Message' in the upper right.
But in case you prefer doing it the hard way (and for the benefit of others), I have pasted the REG file contents below.
If your students are extremely savvy, you could invest in a program called DeepFreeze. With it installed, you won't have to worry about any changes they make because when you reboot, everything is back the way it was. The next day, they won't even find any remnants of what they cooked up. I think it costs about $25.
DeepFreeze:
http://tinyurl.com/5t7gg
Good Luck
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***Warning: Performing manual changes to the Windows Registry incorrectly can make Windows inoperable. It is always advised to perform a Registry backup and setting an XP Restore point prior to making changes to the Registry.***
(involves DWord values set to 1)
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\ActiveDesktop]
"NoChangingWallPaper"=dword:00000001
"NoAddingComponents"=dword:00000001
"NoComponents"=dword:00000001
"NoDeletingComponents"=dword:00000001
"NoEditingComponents"=dword:00000001
"NoCloseDragDropBands"=dword:00000001
"NoMovingBands"=dword:00000001
"NoHTMLWallPaper"=dword:00000001