I just wanted to wish you luck since I don't think I have relevant experience.

DS may be hoping for more than he can get in the PS, but if he stays in the private school and things don't go well he will always feel like he missed a great opportunity to go back. He is old enough to have a big vote in the final decision. I say make sure he has realistic expectations about going back to PS and hope for the best.

Good luck

LMom