- First create all needed folders for the desktop. Name them and position them where they are wanted.
- Logout then back in (this saves the icon positions).
- Go to the Users folder and do a Get Info on the Desktop folder (highlight it and hit Command-I). Change the permissions so the user only has Read Access. Potentially you could change the owner and a group the user belongs to, as this would prevent the user from easily changing the Desktop folder back to read and write.
- Run Terminal, then cd desktop. At this point, it's usually good to do an ls -al (or pwd) to verify you are in the right directory. If you're sure you're there, then type chmod u-w .DS_Store.
A lab I've been working with has one admin account and one student account. Several different classes use the same machine, so we set up folders on the Desktop -- one for the morning and afternoon class for each day of the week, plus for the web browsers, a Downloads folder on the desktop. With the normal OS X settings, any of the students can rename and move the folders around the desktop, or even into other places on the computer.

