Interesting responses. Here's more background.

Son, aged 5.5, homeschooled; no preschool. No TV at home. Good sense of independence. Interested in reading. Does math well.

We want to put him in parochial school. We know the kindergarten teacher has 20 years experience, and this is impressive to the nth degree to me. Haven't met the first grade teacher at all.

It would be a full day situation.

The boy has not been tested, and this is our first: we have no notion of how to interact with school people, or school-related tests.

In my case, at about third grade I was popped into fourth grade in the middle of the year; agonizingly missed my old classmates, and this affected my class work, and so I returned, happily enough, to my classmates. But I did spend a good deal of time staring out the window and raising a ruckus now and then. So I don't want my son to be in that situation, if he would be better occupied elsewhere.