New AP system

I have to say I'm a bit confused over the new AP/IB system at school. From what I've been told, you can take an AP course, but opting out of the exam (which is stated as being optional, mind you) will negate the fact that you are taking an AP course. So my understanding is that AP is the new IB, and since Comprehensive has merged with Accelerated, my only options for classes are IB or Comp. There's no middle ground? What if I find IB a bit too challenging, but find that Accelerated doesn't challenge me enough? What exactly am I supposed to do in that situation?