Collaboration tool for students and teachers
I understand you mean "school" as in "before university", so you are working with non professional researchers. In this case, I think the most important bit is to keep it simple, and use tools people know and are familiar with and just work. So,


Mailing list: for group-wide communication. There are tons of free alternatives.
File upload: shared Dropbox folder or ownCloud. With the extra benefit that everybody has a backup of everything, so nothing gets lost.
Everything else: any free wiki.


That should cover all your needs.