There are as many people that advocate starting children a year later, which is pretty much what you’re thinking of doing by having him repeat a year, as there are people that say don’t do it. That’s a decision only you can make. My only question is if you know he has social skills issues why not get him into social skills training, done in group (you don’t learn to be social by being on one on one in therapy) you learn it through social interactions and redirection by people trained in behavioral modification therapy. He needs treatment so that he can become aware of social cues. It’s not likely to come to him on his own out of the blue. Leaving him behind a year won’t do anything for him, except leave him behind a year, and if he’s bright what is the point of that? My son, 10, struggled with the same thing. Always sad, felt left out, and other negative feelings towards himself. So I found a reputable summer social skills camp, 9 weeks of driving hell because it was far away, 5 days a week. But let me tell you, at the end of that process which he balked at plenty because my son is the type that doesn’t like to hear the word no and will try to negotiate and manipulate you to get what he wants (so he has problems with adults as well), but at the end, he learned to unwillingly comply with instructions from adults and most importantly learned how to read social cues and interact with other children his own age. Does he prefer still to be with younger children? Yes, and I let him. But the important thing is that he learned and can interact with his peers when he wants to, which was the goal. As to the adults, that’s next on the list. In this house, the therapy never, ever ends.