[pyroslev]

Like everyone, I've seen what one person can do to lead to the downfall of a team. I think you guys are in a position that if you act properly and most importantly, fast, you can still pull the situation out of the fire. Everyone's advice thus far is mostly spot on. General strike won't work given the time you got left and the situation. Kims and Roger are pretty much on the mark. Here is how I'd handle it.

Go up to the highest school level supporter you have. Principal up to the School Board.
Take as many people as you can but insure that they are level headed. Those that are not, get their feelings and grievances in writing. (Bad timing in an outburst of emotion is a nail in the coffin.)
Bring the mentors, those still with you and those that have walked, into it similarly. (adults listen to adults)
Another avenue would be to bring the state/district level FIRST group in. Example would be if you were in Virginia to get in touch with someone in VirginiaFIRST. (Help from people in FIRST isn't a bad thing.)
Another local, parent or child team's support too would be great. (teamwork.)

I hope that you can get this issue resolved soon. I've seen to many good teams fall victim to politics, be it from one individual or a group. Good Luck and stay strong.