common directory with group controlled acces for multiple users

[Alain Muls]

Hi

I need to setup an account on my server for 3 students so that they can have 
access to executables and scripts for processing daily GPS observations. Since 
I want only 1 copy of these exe/scripts, I am thinking about setting them up 
in /usr/local/share/gpsprog dir and I want to set the s-bit on the group, so 
that I have

rxwrws---     /usr/local/share/gpsprog

Now if one of the students modify a script, the others should have access to 
this dir. I think I should set something similar to umask for these persons. 
How can I do that?

Also in this context, I wonder whether I should grant them a graphical login 
(if so, how) or a ssh login, which does not give them a menu perhaps causing 
them to get lost.

Any advice is greatly appreciated
Tx/Alain

PS: the PC is run by Kubuntu 3.5.9 (or .8?)