Help needed on setting up a WinXP computer as part of classroom setup

I'm working in a classroom, and one of the teachers would like me to
set up a WinXP computer (it will be part of the workgroup set up in
the classroom) so that:

- It has 4 users (corresponding to the teachers)
- Students may only send (not delete, edit, or overwrite) their work
to any of those 4 users over the network
- A teacher may only view files sent to them (not the others)

I'm thinking of something like using password protected folders or
something like it for this purpose... if anyone has any specific
ideas, pass them along.