The videos show eight cheerleaders at Denver's East High School repeatedly being pushed into splits while their arms are held up by teammates, KUSA-TV reported Thursday.
In one video, a girl repeatedly asks her coach to "please stop." The station says the videos were shot on the phones of two team members and were sent anonymously to the station.
Denver Public Schools superintendent Tom Boasberg called the videos "extremely distressing."
"We absolutely prohibit any practices that place our students' physical and mental health in jeopardy," Boasberg said in a written statement. "We do not and will not allow any situation in which a student is forced to perform an activity or exercise beyond the point at which they express their desire to stop."
The East High School principal, an assistant principal, the cheer coach, an assistant cheer coach and a district lawyer were placed on leave during the investigation, Boasberg said.
The Denver Police Department said child-abuse detectives were investigating.
Jim Lord, director of the Cheerleading Coaches and Administration Association, told the station the videos show practices that are outdated and damaging.
Lord said forcing athletes into painful stretching used to happen decades ago. But he said coaches are now required to learn safe stretching practices.