“Shake off the stress of school,” coach Fernando Restrepo called out to his jiu-jitsu students as they circled the Bronxdale HS gym, their bare feet slapping hard on the mat-covered floor.

After an intense warmup, it was time to teach the students a new move: the paper-cutter chokehold. “It’s a move that looks like the paper cutter in the art room,” coach Restrepo explained in both English and Spanish to the students in a “we mean business” tone of voice.

He modeled the move on a student, bending his elbow and moving his arm up and down over his opponent’s Adam’s apple. Then students, working in pairs, tried the move.

Brazilian jiu-jitsu — a new form of the traditional Japanese martial art — is a twice-a-week, after-school program open to all the students in the five schools that make up the Christopher Columbus Educational Campus in the Allerton section of the Bronx. It was started last year by Restrepo to build student discipline and self-esteem.

Unlike judo, this form of martial arts emphasizes ground-fighting techniques. It employs joint-locks and chokeholds to maximize force using mechanical advantage instead of pure strength.

“Jiu-jitsu gives confidence to the humble and humbles the tough guys,” Restrepo said. “This is about technique, not strength.”

A former social studies teacher, Restrepo is now Bronxdale HS’s restorative practices coach, responsible for helping students and staff to create a more caring school community.

“I support programs such as jiu-jitsu, peer mediation, youth court, advisory, achievement mentoring and peer group connection so that students feel more connected to school and are less likely to cause conflict in the community,” he said.

For jiu-jitsu, Restrepo is assisted by coach Michelle Colon, a computer teacher. Both are brown-belt jiu-jitsu masters and are working toward black belts.

The program has been a hit.

Pint-size senior Amy Ngo, a dynamo on the mat, said she signed up for the activity “to step out of my own comfort zone and try something new.”

Junior Celine Cordero, a member of the volleyball team, wanted to “find discipline and use my body differently.”

Senior Michael Gardinez admits his mother was right when she urged him to give the sport a try: “It’s been an amazing challenge.”