It could be that the modern noisy classroom with group activities, incredible amounts of motion and distraction and little isolation are not positive environments for those with autism or Asperger's. I'm just not buying that autism isn't a bigger problem than it once was....and it isn't just criteria for the diagnosis.
Autism is showing up in families that are wealthier and more educated than average. It could be they are more determined in getting the tests done, won’t take no for an answer, or happen to have children later in life and maybe that is a cause. Think about some of the strange kids you went to school with, and wonder if maybe they were undiagnosed. I Know I would be diagnosed as having ADHD if I were in school now, but back then I was just a prone to daydreaming.