(sorry for my bad english)
there is a solution similar to classroom extension in smoothwall?
This?
http://www.ipcop.org/2.0.0/en/admin/html/proxy-cre.html
We’d need a custom web page to manage the classroom.
@stephdl what do you think? 
I have a go and I can set by db command either for a group or for a particular user to use specific panels of NethGui.
do you want a panel, or we let this kind of settings manual ?