It really can vary by school. Our son was going to a highly regarded elementary school in Fairfax County (which many feel has excellent schools) when we noticed something wrong with his performance. Turned out he had ADHD and OCD. However, it took us a couple of years, and thousands of dollars in attorney's fees and testing fees to determine that; the school absolutely stonewalled us. And in this case, it was just one person--the principal.
On the other hand, when he went to intermediate school, the picture changed radically. The school was supportive. It understood special education. It followed the law regarding special education. The difference was night and day.
You'll find that some schools have reputations for being very good for children with disabilities or learning issues, and others are horrible. And it's not necessarily upscale schools versus those serving a more diverse student body.
So: Do Google searches on ADHD and Aspergers to identify the groups serving those communities (if you haven't already; you probably know the groups). Find the chapters serving your community. Contact them. Ask them, point blank, which are the good schools and the bad schools. (From a Realtor's standpoint, I can't describe one school or school district as good or bad; I'll point you to some standardized statistics that probably won't tell you much. From the standpoint of an ADHD child's parent, I'm more than happy to share my opinions. And, luckily, non-Realtors aren't bound by even those constraints.)
Hope that helps.