Depending on the kid.
I personally practice Muay Thai, Minor Kempo, Minor Karate, Kickboxing, and a bit of Taekwondo.
Depending on their ages (around 6), it's mostly just body builiding, from light jumping, how to punch/kick correctly, running laps.
Older kids (10+) get taught harder things, like elbow strikes, knee strikes, and jumping moves.
The older ones (over 15) get taught knife combat: Being unarmed and dealing with armed opponents, how to properly use a knife, and literal grappling to avoid injury against an armed opponent.
Then I have a special sub section who I teach swordsmanship when I have free time.