Brazilian Jiu-Jitsu (Portuguese pronunciation: [ʒɪwˈʒitsu], English: /dʒuːˈdʒɪtsuː/) (BJJ) is a martial art, combat sport, and a self defense system that focuses on grappling and especially ground fighting. The art was derived from the Japanese martial art of Kodokan judo in the early 20th century.
It teaches that a smaller, weaker person can successfully defend against a bigger, stronger assailant by using leverage and proper technique—most notably by applying joint-locks and chokeholds to defeat the other person. Brazilian Jiu Jitsu training can be used for sport grappling tournaments (gi and no-gi) and mixed martial arts (MMA) competition or self defense
More importantly it give the kids focus, and opportunity to burn off some energy and self discipline