The teacher, Uma Maheshwari, 41, who also taught Hindi language to high school students, was attacked by the boy as she was getting ready to teach a special class Thursday morning, the Times of India reported. She was pronounced dead at a hospital.
Police said the student at the St. Mary's Anglo-Indian Higher Secondary school in the southern city told them he had been under pressure after as his teacher sent adverse remarks about him to his parents, and that he felt he would not be promoted to the 10th grade, the newspaper said.
Police said Maheshwari was stabbed repeatedly in the neck, chest and abdomen. Another student told police the attacker had the knife wrapped in paper, the Times said.
Investigators said the youth had purchased the knife from a nearby shop and took it to school for three days, waiting for an opportunity to attack his victim.
"He couldn't attack the teacher as she was always with some students the last couple of days. On Thursday, she was alone in a classroom when he stabbed her," a police officer said.
After the attack, the student was overpowered by other students and school workers. He was described as non-aggressive and aloof.