We've been meaning to do it for some time, but we finally got around to it - the Unknown Son finally took his first Karate classes. We figured that it would help his strength, coordination and balance, and give him something of his own to do that's not shared by his sister.
In addition, he's a very small, smart kid (about 5th percentile in height and weight and 95th percentile in reading and math). So that means he'll probably eventually have to deal with bullies. I know this from experience, since I had a boy in my 3rd grade class that would literally kick by but halfway home on a regular basis. That's not a figure of speech - he live halfway between the school and my house, and would often "escort" me as far as his house. Every few steps, he'd plant a boot in my butt.
But anyway, U.S. had a great time. The first class was a private one with an instructor, and he was great. He made U.S. do some exercises, a few punches and kicks, a lot of jumping and physical activity, and gave him a basic orientation top the school and how classes worked. It was cute seeing him learn how to stand at attention and bow correctly (all with a lot of enthusiastic shouts of "Yes Sir!" and "No Sir").
The school (dojo) is one of the largest in the Northeast, and has over 300 kids enrolled, all who come twice a week. So, it should be good not only for the physical training and self-defense aspects but also for the friends he'll make. There are probably 30-40 kids in U.S.'s elementary school who go there, so he'll have a lot of reinforcement (not to mention well-trained friends if he ever needs a helping hand).
And he looked so proud with his white belt (the "beginner's" belt). He's excited at the prospect of possibly being able to test for the next level (the "yellow") belt in only a few months.