No kids, but I started when I was 6...October birthday. As an elementary school teacher(24 years), I saw so many immature boys all the way up to 6th grade. 6th grade, kinder, & first grade boys were where I saw so much stupid going on. I get it when your are 6 & 7 years old, but come on man, when you are 12 !!! A lot of girls in k-3 were more mature than some of the 6th grade boys I had to have a coming to Jesus meeting !!
If you're debating on when to start your kid in school, it's never a bad move to wait a year. Heck down here in Texas ( in my former school district that is one of the legendary TXHSFB programs) many athletes are "redshirted" in 7th grade !!