Hmmm - Jenna likes banging us with her head, and pulling my hair, so while its not kciking, its the same control thing.
It has got better - purely from just ignoring the behaviour. She loves it when I say "ouch" so I just had to stop doing that. I also sometimes would hold her head and say "no - that hurts mummy" but I'm so not sure it did anything.
I think boys have a tendency to be more physical at an earlier age than girls, so while its important to try and cut it out, they will always be a little rougher. I think you have to let him know its not OK, just how you do that is another question. Can you change your reaction to something different? Using different words etc? Rather than "no" maybe say "kicking is not OK - please stop that now".