At Boston’s Joseph J. Hurley K-8 School, students in Mr. D’s class might be subject to WOD-like penalties.

Forget something in your locker at the beginning of the year: two push-ups. Do it in January: four push-ups or 10 squats. Curse in class: 40 push-ups or 200 squats.

A member of CrossFit Southie, Mr. D brought the kids to the affiliate for an afternoon of working out, camaraderie and community.

“I think a lot of people in today’s world like to think with kids, ‘Let’s take out the competition from their physical activity.’ No. Life is competitive,” he explains. “And the reality is you’re hired or you’re not. You are getting the promotion or you’re fired.”

Because there’s no dedicated physical-education time or gym at the public school, CrossFit Southie is a great option for his students, Mr. D adds. It teaches them quick thinking, he says.

“If you want to bring stuff like this to your program, it’s gonna take a lot of work,” Mr. D says. “Find a box near you. Impassion them. Inspire them to think about the good that it will do for the community.”