Just saw a message from cprofitt that "[w]e have some new folks in our group that are looking to get information on how to run an Ubuntu lab." I didn't see any pre-existing threads on this so I'm starting a new one.
Here's what I do:
I give students complete freedom, no restrictions. That means they have the ability to mess something up so bad that the machine won't even boot. That's ok. When I first started messing with Linux, you know how many times I completely trashed the system and had to reinstall before I could keep the machine stable for more than a week? Probably about 20 times, no exaggeration. Now, Linux has come a long way in that time, so screwing things up that badly is quite a bit harder, but I think students deserve the same chance to mess up that I had.
I think the only cost to the students of messing things up should be having to do the reinstall themselves or restore the machine to an image of a working system. (Once I get a machine working just how I like it, I make an image with Clonezilla and on newer machines, it only takes 20 minutes to restore that image and get it working perfectly again).
So that's what I like to do. If anyone has questions, I'd be happy to answer them. What the the rest of you do?