Karate... with or wihout black belt?
Karate Kids is actually Taekwondo and not Karate. Taekwondo is a show sport and in my personal opinion many of the moves are more about appearance than practical. They wave the registration fee, which every dojo does. You pay for the outfit ($50 if I recall). Then the fun begins. Its only about $120 per month to join. They mention the Black Belt program, but it's not pushed heavily. During the white belt phase the Black Belt program iniates are picked out. In the Black Belt program kids (even as young as 5) are given sword and other weapons. The gear costs an additional $500 and the monthly fee jumps to above $150. Which is fine if you want your son to play with swords. After the first belt test the pressure to move to the"program" starts to build up and majority of the marketing is focused on the kids. Those that are not in the program feel like outsiders.
Later I was told that you cannot continue to black belt without joining the program. When I made it an issue, then suddenly there is a way. Now the teachers themselves are good and if you feel that your kids are fine learning weapons at 5-8 then I am sure that you will get your moneys worth. If you want your kids to learn practical self defence without weapons at a price range that you are personally comfortable with then I suggest going for an actual karate studio.