The teacher, Saroj Das, allegedly clicked some obscene photos of the girl some months ago and started black-mailing her with them.
He has been raping the girl for the past three months, according to the police complaint lodged in this regard.
Police said the girl did not want to go to school for sometime, and after much persuasion by her family members, disclosed everything yesterday.
Her family members lodged a complaint with Bagdogra police this morning and the teacher was arrested.
The girl will be sent for medical tests at the North Bengal Medical College and Hospital tomorrow, police said.