A case has been registered against the teacher, they said.
The boy was studying in the 12th standard at a private school near Pattukottai in the district.
The incident occurred yesterday.
The boy's relatives alleged that a teacher had scolded him for reaching the school late.
After returning from school last evening, he went to his room and an hour later his mother found him hanging from the ceiling fan, police said.
The relatives staged a road roko on the main road demanding action against school authorities.
Police assured them that a case would be registered following which they dispersed.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)