Is he at a private school that works with SN? If so, they might be able to suggest othert such private schools that are a better fit. Have you considered hiring an educational consultant. What public school system are you looking at? Does he have a just in case IEP? if not, I would start the process as a back-up.
If it's the right fit I don't moving schools is disruptive. I just think you need to do all the legwork to make sure you get a good fit before leaving.