A “mild-mannered” high school wrestling coach allegedly snapped over the irritating social media “six-seven’’ trend — and slapped a student athlete for cracking a joke at practice.

Steven E. Nelson, a math teacher and the head wrestling coach at Connecticut’s Norwich Free Academy, allegedly thought the student was slacking at practice while working out on a stationary bicycle in December — and told the boy to increase his speed from 30 rotations per minute to 60 or 70.

“Coach, six-seven,” the student chirped back, referencing the exhausting, nonsensical slang term rampant among Gen Alpha, according to an arrest warrant unsealed Thursday and obtained by the CT Insider.

Nelson had apparently had enough of the irritating social media trend and allegedly hit the student in the face with an open hand in response.

The student told investigators later that he started crying and told Nelson not to touch his face.

“Oh, I got you good, is that why you’re crying?” Nelson taunted, according to the arrest warrant.

The teen said he hopped off the stationary bike, packed up his things and walked home. He took a nap, then vomited when he woke up, he said.

The boy’s father took him to the William W. Backus Hospital in Norwich, where he was diagnosed with head trauma and a concussion. Police went to the hospital and confirmed the teen had a mark on his left cheek about 1½ inches by 1½ inches, according to police.

Nelson insisted he only “tapped” the student in an effort to get him to focus, authorities said. He added that he might have meant to hit him on the shoulder but caught his head instead, according to the warrant.

Other student witnesses corroborated Nelson’s account of what happened, according to the warrant.

A wrestler who did not see the incident described Nelson is a “good coach” but who can be “rough,” the warrant said.

“He is mild-mannered, he does not have a hot temper. He is so supportive of the kids,” said Lisa Zeppieri, who has a son on the Norwich Free Academy wrestling team, about the coach to WFSB.

“He’s a great guy, I know the kids miss him, and we can’t wait for this misunderstanding to be resolved,” she said.

In a follow-up appointment with the student, a neurologist confirmed that the teen suffered from nausea, ringing in the ears as well as depression, according to the warrant.

Video footage from the school obtained by investigators allegedly shows Nelson and the student wrestling twice at practice before they moved to stationary bikes. In one of the bouts, the coach “used his elbow to make repeated contact across the victim’s head,” the warrant said.

The coach said the teen never complained about being injured during practice when he was interviewed again by police in February.

Nelson was placed on paid administrative leave Dec. 31, the day after the incident.

He was charged with third-degree assault and risk of injury to a child April 16.

He briefly appeared in court for his arraignment Thursday, with several supporters in attendance.

“He is mild-mannered, he does not have a hot temper. He is so supportive of the kids,” said Lisa Zeppieri, who has a son on the Norwich Free Academy wrestling team, to WFSB.

“He’s a great guy, I know the kids miss him, and we can’t wait for this misunderstanding to be resolved,” she said.