MONTVILLE, Conn. -- A former substitute math teacher is charged with supervising a student "fight club" at a Connecticut high school. Police say cellphone videos show 23-year-old Ryan Fish encouraging students as they slap each other in the middle of a classroom at Montville High School.

Fish pleaded not guilty on Thursday to charges including reckless endangerment and risk of injury to a minor.

He has denied facilitating the fights and says he thought the students were just being "rambunctious."

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Fish was fired in October.

Police began investigating in December after a student told a social worker he had been beaten at school.

Superintendent Brian Levesque tells The Day newspaper he didn't alert police after firing Fish because he knew of only one fight and thought it was an isolated incident.

CBS Hartford, Connecticut affiliate WFSB-TV reports an arrest warrant says Fish watched the students and even moved trash cans out of the way so students had room to fight.

According to the station, when police asked Fish what happened during class, he told them he "would let them be teenagers and let them get their energy out."