Out of curiosity, have you ever monitored and been in charge of a playground full of kids?
I've had to monitor gyms filled with kids and outdoor play at homeschool cooperatives and group meetings. There were only a few parents who disagreed (even argued) with me because I'd stepped in and/or stopped a "game". My reasoning was: If your child gets hurt when I'm on duty, who are you going to blame?
I had only ever monitored my own kids until assisting and then teaching 4th grade at a Christian school. Boy, was I in for a surprise. The kids do the goofiest things, as if they are trying to get hurt!