Here's one crossing guard you don't want to cross.

Gerald Kelly, a 6-foot-2, 200-pound crossing guard at Drexel Hill Middle School was arrested last week for beating up a 14-year-old boy who'd called him names, according to police.

Kelly, 60, was off duty and coming out of the Shadeland Pharmacy, on Shadeland Avenue, Thursday afternoon when he saw the teen sitting on the steps outside, Upper Darby Police Superintendent Michael Chitwood said.

"During the school year, the victim apparently had challenged this guy, calling him 'fatso' and 'fat man,' " Chitwood said. "But on this day, as far as we know, he wasn't taunting him."

Still, Kelly allegedly "went after the kid," kicking him, knocking him to the ground and putting his foot on the teen's throat and chest, police said. The assault was witnessed by several adults, according to Chitwood.

"I certainly wouldn't want this guy crossing my kids," he said.

The victim did not require hospitalization but did suffer a bump to the back of his head when he fell to the sidewalk, according to police.

Chitwood said he was shocked when he took a look at Kelly's background and realized that he had an arrest record dating from 1971 that includes assaults, possession of a firearm and possession of an instrument of a crime.

Most of the cases against Kelly were dismissed, but he did serve time in county prison on a theft case, Chitwood said.

Aside from saying that Kelly was hired last October, Upper Darby School District spokeswoman Dana Spino declined to comment on the case or the district's hiring policy for crossing guards.

Kelly, of Shadeland Avenue, has been charged with simple assault and harassment, Chitwood said.