A Senthil Kumar, working in a government school in A Pallipatti molested the children, all aged about 13 years, they said.
Kumar was detained following complaint from the students that he had molested them, a senior district police official said.
"We are questioning the teacher and have registered a case under the POCSO (Protection of Children from Sexual Offences) Act against him," the official told PTI.
He said the teacher would soon be arrested and produced before a court.
