The 12-year-old victim alleged that Krishna Shankar Singh had similarly molested at least 35 other girls from the school.
"The victim, who studies in the class VI of the civic school, is the daughter of a political party worker and approached us with a complaint," said an officer at Dahisar police station.
The girl claimed that Singh used to make her sit on the last bench as she was not well-versed with English and would come over to her bench on the pretext of helping her write better, grab her hand and touch her inappropriately, the officer said.
Singh was arrested today and will be produced before a metropolitan court tomorrow.