I don't have the experience of special needs that you have, but I have asked a school for exactly the same thing some years back - please just teach my kid in his socially appropriate class. I have since learnt how this just isn't the done thing in most U.S elementary schools. To us, what might seem a very reasonable request, is to many teachers/schools something quite alien. I wish you so much luck, but want you to be aware that the school's attitude is quite genuine, and that you are proposing a scenario of 'extreme' differentiated teaching that many educators are very uncomfortable with.