Mac OS X (10.5 and newer) has a feature to enable a guest account. The guest account has no password, is created afresh on each login, and is deleted on each logout. Users can, of course, connect to their file shares and access their documents. [It is a very poor scenario for working on multimedia projects, but it doesn't sound like you are trying to do that.]
Here's a guide for turning a guest account on on a single computer. If you have a preference management system in place (using, say, configuration profiles, or workgroup manager + open directory), you can manage the setting for all the computers in your lab. Some of Apple's articles for educational institutions may prove useful in this regard; "Tips and Tricks" covers the now-deprecated Workgroup Manager, and the remaining titles will point you in the right direction if you are using configuration profiles or active directory.
If that is inadequate, it is also possible to use a login or logout hook to run a script to copy (or rsync) a template folder for users to use (and I can provide more details if you'd like).