K.,
I'm not sure that I have enough information to give an opinion. For instance, do you work outside the home now? Are you thinking about a part-time preschool that's only a couple days per week?
I don't think it's ever too young to do preschool type activities. But, I don't believe a child that won't be in K. for 3 more years needs to be in a formal school setting for 8 or 9 hours per day if the mother isn't working.
It also depends on what type of school you intend to send him to. So many public school classrooms are illequipped to handle the children that come to school ahead of the pack. These teachers spend so much time trying to catch up the children that don't know anything, the smart kids get bored. I've sent a lot of my daycare kids to school knowing how to put together simple words, writing those same words, able to cut paper, glue, color, draw, listen to stories etc. And yet, many of these same kids have hated school later because they were not in the right environment for them.
Our oldest daughter was in school longer because her birthday is at the end of the year. I believe that being in school held her wild ways off just a bit longer and helped her to mature a little more before she was able to do any real damage to her life. Our second daughter turned 18 just before the end of her senior year. With her new grown up independence falling at graduation time, she was feeling her wild oats a little too much and made a very huge mistake that she will be paying for a very long time. Maybe timing had nothing to do with it. But I personally want to keep them at home and in school for as long as possible. 18-20 is a difficult time period in a persons life.
If you send your son early, he may be bored. If he moves up to a higher grade because he knows a lot, he will graduate early. Everyone has their own ideas on this. But I think they have plenty of time to grow up.
Also.. Are you more concerned about his social skills or his academic ones? You could find a happy medium. How about finding a daycare that offers preschool only an hour or so a day or a few hours per week? Then your son can have a family apmosphere without having to fall behind academically.
Suzi