The Class XI students of Panapakkam Government Higher Secondary School at the nearby Arakkonam town jumped into a farm well at Nangamangalam village yesterday.
Fire and Rescue Services personnel fished out the bodies and sent them for autopsy to a government hospital last night.
"Based on the preliminary inquiry, the headmistress and class teacher have been suspended," a district education official told reporters here today.
"Four teams of police personnel are questioning the class students, teachers, and others and only after the conclusion of the enquiry would the cause of the suicide be known," he said.
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The official said no suicide note had been recovered.
He said a preliminary enquiry revealed that 11 students were chided by teachers for not being attentive in class and were asked to bring their parents on November 24.
"Yesterday, out of the 11 students, seven apologised and assured the teachers that they will be attentive. The other four students ended their lives," he told PTI.
Of the four girls who committed suicide, two came to school in the morning and left the premises immediately.
They later joined the other two and all of them went to the farm in their bicycles.
"Local people, including a cowherd, saw the girls going to the farm well," he said.
Villagers alerted police and local officials after they spotted the abandoned bicycles near the farm well.
Senior police officials and a district official placed wreaths on the bodies.