Looking for a story about a teacher teaching self-defense to girls

Hi, I remember reading a story on this subreddit where a female teacher was teaching self-defense to her students in a park during the summer. The story involved guys who had gym bodies and were tied down, possibly from a prison (if I remember correctly). The teacher was instructing the girls to target a man’s weak spot by kicking them in the testicles.

I’ve been searching for this story but haven’t been able to find it. If anyone knows the title or has a link, I’d really appreciate your help. Thanks!