Plugin for school club collaboration

We have a school club that we’re setting up a site for. I’m looking for a plugin that can be set up to:

* allow kids to collaborate, share files and maybe conversations (like in a forum)
* be password protected for sub groups; for example the club has 4 groups of 3 kids each, each group of 3 kids would have their own section of the plugin that other groups couldn’t get into (to prevent ‘cheating’)

I’m thinking it would sort of be like sub-forums in a forum plugin, but can’t seem to find an appropriate plugin.

I hope that all made sense, difficult to explain! Thanks in advance.