My second grader (in Arlington) is dyslexic and is receiving SpEd services. I know this doesn't help you, as you're looking for middle schools, but FWIW we receive phenomenal services. That said, I think a lot of the things that make me most happy are directly related to the lead SpEd teacher at our school (Nottingham) so I don't know how well that would transfer to other places or if what she does is just "her" and not the system.
That said, good luck, and I'll be watching this thread with interest to see if anyone has anything, positive or negative, to say about our future middle school (Williamsburg).