Ramana Murthy, an English teacher, was showing pornographic clip to female students on his mobile at a government high school in Rajam in the district, an official with Rajam police station said.
He was also allegedly behaving in a vulgar manner with the girls. The parents of the girls caught the teacher and handed him over to the police, he said.
He has been arrested and a case under relevant sections of IPC has been registered, police said.