Some people are focused on sports and want their kid to be bigger than their classmates. So you either opt out of school if the birthdays work, delay kindergarten if it isn’t mandatory, or send the kid to a private kindergarten and have them repeat.
It’s a big advantage, especially around 11 or 12, and get kids on more competitive teams earlier.
I coach little league, and we see it all of the time. It’s a compliance issue as kids get a little older and start playing tournaments.
Are teams not based on age in the United States? In New Zealand they're all categorised as 'under 9s', 'under 8s', 'under 7s' etc. They've also introduced weight classes to a lot of teen sports too to prevent them from being dominated by gigantic Samoan kids.
School teams are classed by grade level. Non-school teams are by age. Non-school teams are generally seen as a fun thing to do on weekends, while school teams can become very serious. Hold your kid back early and they will be the star of the team 12 years latter. Some of this is because at some critical points their body is physically better than their peers and thus they get to play a little more and get that much more practice. Some of it is the parents who think doing well in sports is important are teaching their kids young to play sports and so those kids are getting practice at home that other kids do not get.
On a similar note, I've read about parents in China scheduling the conception and birth of their child so that the child can be the oldest at school. Although it's only a few months' difference, but in kindergarten and elementary school, that head start could mean quite a difference in academic performance.
I wonder about this also. In most districts you don't have a choice, and it is those kids with October-December birthdays that are delayed a year because of the cut off date. Maybe they are using fake birth certificates?
It’s a big advantage, especially around 11 or 12, and get kids on more competitive teams earlier.
I coach little league, and we see it all of the time. It’s a compliance issue as kids get a little older and start playing tournaments.