I say quit talking to other parents and the teachers in the garden where the tomatoes are rotting! Just decide what you want and go for it. Do you trust the psychologist or the parent on the corner? The only person I'd ask is the K teacher, and at that, I'd keep in mind her perspective. You don't need all her judgment, just an opinion on academics and maturity. I found that when you invite others to judge, they will. Once you have done it, if he fits in (sounds like he will), nobody will notice.
If you have school sponsored sports and your child is destined for varsity, that is something to consider. We are coming upon that now, but would not have made the decision any differently.
One of mine skipped--the earlier the better.
