Mostly I trust his instincts. But in this situation, I think that the paradise lost thing is active in his mind. I would like to let him choose, as he's the one who has to get up and go there every day, but I want to be sure that he hasn't built up an unrealistic picture in his mind of how great the public school would be. I worry that his current school is more 'accepting' of offbeatness, although for all I know, they could be worse than the public school. I know that this year the begining of school was stressful, and that the teachers who were new to him didn't 'get him' and he didn't 'get them' but then after about 6 weeks something clicked and he's been about to be responsible for his homework and classwork, even with the new teachers.
So, is returning to the public school, one year advanced, 'social suicide' as my son would put it?
This passage of your original post is what's standing out most to me. The real crux of the issue seems to me to be--far more than the academics--how realistic your DS is about his potential social life at each of the two schools.
Am I reading that right? Or is the academic level of public school of concern as well?
If I am reading you right, then I think it is your duty to make him as sure as he can be that he's not experiencing selective memory about public school.
(BTW, I just typo'd "pubic school," which would be a whole different problem!)
Anyway, poke him and prod him and make sure he's sure...but if the social scene is really the big issue, then I think you do, ultimately, have to let him decide. He is the one who has to survive his social life.
If he chooses public school, then I'd start scoping out kids from public school who are in the grade he'll be joining next year. Anything to grease those social wheels.
Now I'm going to re-re-read your later posts to be sure I didn't miss some vital point...