Karate for kids
My daughter started to learn karate at age 6, too. It wasn't long before we noticed improvements in her concentration and learning at school and in her self-confidence, not to mention in her fitness. This inspired me to find out more about it for myself and, six years later I am still training.
Although my daughter, now aged 12, is taking a break from karate to develop other interests, including hockey, the years we spent training together gave us a shared interest and it would be worth considering taking an interest yourself and maybe training with your child - I certainly haven't looked back.
There's a great book published here in the UK called Karate for Children - written by Shihan John van Weenen and this has certainly encouraged a number of children that I know to train regularly.
Hope this helps.