Sebastian Selvaraj, the history teacher of a private higher secondary school here, had asked Prakash and 11 other students to stand outside the classroom, police said.
Prakash then went to the school laboratory, poured kerosene on his body and set himself ablaze, they said, adding Selvaraj has been arrested.
The teacher claimed that he was under pressure from both the management and officials to ensure better performance by the students but they were 'adamant' in not studying well and following classes, police said.
District Collector Malarvizhi and the Chief Education officer visited the school to inquire into the incident.