I have a kid age 9. I feel that when he does free kicking it is very slow. How can he improve his freestyle kick?
The key to improving freestyle kick is to do plenty of it at a good intensity.
I would start with sets of 25m kick fast and then build up to sets of 50m kick with the same intensity.
Your son needs to ensure that his knees go up and down past each other when he is doing freestyle kick. This means that he is kicking from the hip rather than kicking from the knee.
The Swimming Expert