Here’s a recent article in the Times about Martial Arts and specifically Taekwon-Do helping to boost brain power in kids.
Here are some other articles on how martial arts can help children:
https://bestforthekids.com/benefits-of-martial-arts-for-kids/
http://www.kenneymyers.com/blog/10-reasons-martial-arts-benefits-kids/
http://everydaylife.globalpost.com/benefits-taekwondo-kids-12644.html
http://www.additudemag.com/adhd/article/3596.html