What's a good martial art for kids to learn

It depends on the purpose of the child. If it's not a professional purpose, it's fine to start at 6 to 12 years old. Not necessarily martial arts, gymnastics or dance can be. The main purpose is to be in the childhood stretching and tumbling movement training. If the purpose is to be a boxer, not a martial arts gloves competition, tumbling training is not too important.

To train real martial arts, there must be sparring practice. This is only safe to do after development. That is, training before the age of 13 or 14 (for boys) is mainly just the basics. Japanese Judo is also good for training basic body instincts for wrestling and balance.

If the goal is to be professional, starting at age six to eight is best. If it is too early, the child's mind is too immature, making too much physical and psychological pressure, more harm than good.