I hate to say it, but if I were you, I'd ban minors from my gaming group as quickly and quietly as possible. If that meant I couldn't have a gaming group, so be it. There's always PbP, you know?
I know, it's not right or fair or anything like that, but sometimes pragmatism just has to prevail. If anyone files a formal complaint (and it sounds inevitable at this point, IMO), then you'll have a tough time keeping your career.
Very sad, but very true. I won't repeat what you already know and what people have already said about the ongoing witchhunt against teachers -- President Clinton had an easier time maintaining his privacy than most schoolteachers do.
Anyway, I'm all for taking a stand against injustice, but I wouldn't choose this one. People don't understand gaming well enough for it to be understood as a "stand," for one thing. For another, what's at stake (a hobby) versus what's at risk (a career) just isn't enough -- I've been without a RL gaming group for a while now (mainly because I can't hold down a job, place of residence, etc...

)... There are other options (I'm a massive fan of PbP myself, though it's hardly to everyone's taste), and even if none of them fit you, well... I'm assuming the being a teacher is far more important to you.
In short, let it go. It's not right, but it's not worth fighting over. Of course, that's just my opinion & judgment... If you choose to keep going, well, I respect your courage, and definitely wish you the best.