If you have an IEP and the school cannot provide what he needs, you can request that they pay for a school that can give those provisions. You need to check your state laws. I think that here where I live, you need to give them advanced notice in writing (a certain number of days before switching schools). If they do not agree and they can't provide what he needs, you can go to mediation or due process. You would need to prove that they actually can't provide the services, and that the other school really can.