I did a few classes when I was younger, but was too lazy to continue. A kickboxing club opened up in my village when my sons were 6 and 9. They both took to it well, within a year my eldest son was in the adults class as Andy his instructor said he hits like a man. They both progressed to black belt and both entered many competitions, both were multiple time regional champions, Scott my eldest is a multi time national champion, Kyle was a national champion once but had multiple Silvers, the way the categories were was to Kyle's disadvantage as they were by weight and age groups with a gap of two years, so with his birthday being in December he might have been fighting someone almost 3 years older even though they qualified for that category by having a birthday in January, I know what I mean lol
They both qualified for a world championships, with Scott getting Bronze and Kyle getting Silver, they never went to the worlds again as it was all about money making, us as parents even though we had paid for the package to go over with them also had to pay to spectate. They were great but gruelling days which stopped when they started work and found beer and women lol