The parents of the three students called officials at Hedrick Middle School in Lewisville, accusing the 26-year-old coach, whose name was not reported, of the incident, WFAA-TV, Dallas/Fort Worth, reported Monday.
"I do know the students said they felt pain," said Lewisville police spokesman Capt. Kevin Deaver.
The coach, who has been on the job for two years, is currently on paid administrative leave while Lewisville police investigate the incident. He has resigned for the next school year.
Lewisville police said the coach could face charges of injury to a child if the allegations are substantiated.
"We certainly wouldn't want someone to face charges if they didn't commit an offense, so we investigate all of these thoroughly," the Deaver said. "If there's one victim, one witness, or three victims."
"He was nice to everyone; everyone liked him," said sixth-grader Elise Leon. She and others said the coach frequently engaged in horseplay with some of the boys at the school.