Roaming profiles...... don't do it!!
You can get Active Directory (well, Group Policy) so that all users get the same profile.
This has a number of advantages
(1) Users can change the look or wallpaper
(2) Different user groups can have different wallpapers, so you can tell if someone is logged on as a teacher or even the administrator.
Users can easily be redirected to their own folders in GP, so don't worry about that!
What I do (and I find it works)
Map a drive with all shared folders
student can then goto a generic folder i.e. Sports Day or
student can then goto their year group (say 2005) which only students from 2005 have access to, then browse to their folder or to another generic folder for only their year group.
If you're afraid to fiddle, then setup a test network using VM software, and you can play in the the safety of a sandbox!