I'm still left wondering, like what? Your son is asking other children his age whether he can play and they are not saying yes? That doesn't even sound like a statement about him, really, it just sounds as though he's using a different social convention to the one they're expecting. It wouldn't occur to me to suggest to my DS that he should ask other 4-5yos whether he can join in, and I expect that if someone had asked him at that age he might well have been nonplussed. So what is it that you're wondering about?
ETA: sorry, I hadn't spotted that you'd made another post after the one I was replying to. I don't know the book the others mentioned but I hope it's helpful! One thing I'd add is that this is the age when it starts to really matter whether kids already know one another or not; they start to have real friends. If he sees these children infrequently, especially if some of them see one another more often, that may be your explanation.
Last edited by ColinsMum; 02/02/10 01:15 AM.