I'd say that being a little nervous is only natural but that you don't need to be! Taking the school is an excellent way to hit the track for the first time. The coaches at the school (I'm one of them) will walk you through the track rules, etiquette and flags and you will have a classroom session before each ride session. When you are on the track you will have a very specific skill to be working on and your coach will lead and follow you on track. All the coaches pay close attention to ALL the riders on the track and will pull guys in if they are riding above their limits or if the coach feels like they need another tip or a bit of correction, plus the course control and corner workers do an AWESOME job of keeping everyone safe.
This does not mean that you are not allowed to ride fast

As long as you are in control, riding safe and doing the drills you can ride as fast as you like! :rockon:
As for the new BMW's, I have yet to ride one but Keith was raving about them. Yes they have a crap load of power but they can be de-tuned a little (start on rain setting for example) so that you can work your way up and get used to the power gradually.
I guarantee that after the first few laps you will lose all your nervousness and will have an awesome time! Not to mention the fact that you will come away with some pretty cool skills
No need to really prepare in anyway for the class either, just arrive fresh and with an open mind, ready to learn!
Cheers and if you have any questions at all about the school, fire away.
Misti