S.G.
K.,
If your child was a girl, I might say, "Send her". They tend to mature faster and socialize earlier. For a boy I have to recommend not sending him until next year. Of course I do not know your son, however I do know many others who had to deal with this issue. The ones who kept their sons back were happy that they had done so. My step-son was sent on and shouldn't have been. From personal experience I watched him as he was slightly less mature than the others, he followed instead of leading (until he became older), he had trouble with sports because he was smaller until his junior year in High School. He even said when we discussed it once, that he wish he had been held back because he would have been more successful in high school sports. He also didn't want to go to college right out of school and consequently never finished. I am not saying that your son will be like this. It just helps to hear from personal experience. I also think a good pre-school is invaluable.