I studied TKD for a little while, many years ago, and decided it wasn't for me (too many rank = $$ promotions). But my 6-year-old son expressed an interest in it, so I enrolled him a couple months ago. His behavior has improved tremendously (and he was a good kid before). He tested for his first promotion last week, and broke his first board. I can see the improvements in his strikes and kicks week by week. I'd like to teach him Aikido eventually, but he's too young and aggressive right now. TKD looks like it's good for him, and a kid's attention is easier to keep when he's learning flashy kicks and strikes. I hung a heavy bag for him yesterday, and he's been getting his workout on it. It's well worth it to my wife and I.