Most parents, when their kids are of age to start taking extra classes, would opt for ballet lessons for their girls, and maybe basketball or soccer lessons for their boys. Nothing wrong with these at all, but maybe they should also consider martial arts like Judo or Tae Kwon Do.
These activities would still burn off a child's excess energies and would instill discipline in them. What's more, it could very well be beneficial for them in terms of self defense, given the society we live in now. Someday, they need not arm themselves with so much self defense products, especially the girls, in crisis situations because they would be empowered to protect themselves.