Giftodd,
That is an interesting observation. That may be the case, where with same aged slightly younger kids they are able to dominate to make play and activities interesting to them. Where with older kids my son has felt very rejected in the last two days. He has played with older kids before but usually with just one and it's been good, but camp has not been good. He likes that they do more interesting things, but socially he feels completely excluded and when they were working on a group project he was not allowed to participate by the other boys either. Last week he was there but in the 4-6 group, but there were a lot of younger ones so he did not socialize much there either.