How to deal with horseplay as a girl in the future and did I do this right?

So today I was at Karate waiting for the clock to say 4:30 so I can start class. While I watch the kids, I see a 12 year old boy Steve (fake names so no identity slips) on top of a 8 or 9 year old boy Hector. I immediately strictly tell Steve to get off of Hector and Hector walks to a chair. He starts crying and I sprint to him and ask if he's ok. He said his ribs hurt and I walked Hector to the water fountain to drink. I told Hector to do 20 push-ups and I tell a great student, Sally to make sure he does them. Hector calms down after water and walks back to the mats. All while my instructors were changing. After class, I tell, and warn Steve not to horseplay like that or there will be way worse consequences than 20 push-ups.
Love y'all lots,
AwesomeGirl123

PS: Pic for fun.