[SenorZ]

Wow. That's terrible.
As a teacher, and new to running a robotics team, I had to learn the ropes when it came to getting trips approved. Luckily the district folks are very supportive of us having a robotics team (maybe having Boeing down the street helps).
I've still had to deal with people in our office questioning the "excuse" for the absence, but I got an assistant principle to approve all my requests.

I'd say you're best bet is to have any effected student write a report about the educational value of the FIRST Robotics and event attendance. Set up a meeting with an AP or the Principal and present your reports. If that doesn't sway the school admin, go to the district/school board.