I would not hold him back a year for kindergarten. We had several suggestions of doing that with DS9 (summer bday), that he wasn't socially ready for kindergarten. And a suggestion that he repeat kindergarten, that he wasn't socially ready for 1st grade. Well...he wouldn't have been "socially ready" a year later, either.
We lucked out and had the most fabulous kindergarten teacher, and he was quite happy. We are homeschooling now; the gap between the academic and social abilities is too great for school to deal with. But kindergarten worked, and I'm happy we ignored everyone who told us to wait.
