Re: How many of you...?
I had a different director for my highschool jazz band every year. Only one of which actually knew anything about jazz - he was a professional trumpet player.
Based on my experience, I'd say that that is pretty much on par with most band directors (including some of my friends that have gone on to become band directors).
If you really want to learn jazz theory you should ask your band director if he can teach you and the group some stuff. It may be, however, that your director just doesn't know that much about jazz or how to go about teaching it to kids. (in my own personal experience getting kids into improvisation is difficult because it can be akin to reading a paper in front of the class, which I always hated doing)
Here are two ideas i think you should consider:
1) Ask your band director about hiring a jazz musician or group to come in and do a master class during one of your rehearsals.
2) Take private lessons specifically for jazz. (assuming you aren't already)
Hope this helps.