The incident came to light on Friday when the girl told her father about the incident.
The teacher has been identified as Shubh Narayan.
The 13-year-old girl was a student of Nehru Hindi Vidyalaya at Moranhat.
According to police, on Friday, the victim told her father about the incident. The local residents of the area after knowing the incident gheraoed the school and assaulted the teacher.
Later, police intervened into the matter and rescued the teacher and took him to the hospital for treatment.
“On Tuesday afternoon, the girl along with another girl went out of the classroom to drink water but on their way, they met the teacher – Shubh Narayan. The teacher asked the other girl to go to the classroom and then molested her,” a police official said.
The victim in her statement before the police told that after molesting, the teacher threatened her and said that if she tells anyone about the incident then the teacher would send her parents into jail.
An FIR has been filed at Moran Police Station by her parents.
“We have recorded all the statements of the victim and the arrested the teacher from the hospital premises. We will forward the accused to the court. We have also arrested few locals as they were trying to attack us,” said a police official at Moran Police Station.