Remove user Vs info after student graduates

[georgematheos]

Once students graduate, we should somehow reformat the data so that their specific user info is gone.
Probably, something like this would be good:
If all students involved in a Vs session have graduated, delete the Vs session info.
For all other Vs sessions, for every graduated student involved, still note that a student was involved, but remove all information that specifically identifies that student.

I think it would be a bad idea to store this data indefinitely -- once the academy no longer needs the data (once the kids are graduated, what use could the academy have for it?), it seems like a breach of privacy to have the information floating around.