Police said Uma Maheshwari, 40, a Science and Hindi teacher at St Mary’s Anglo Indian Higher Secondary School on Armenian Street in the northern part of the city, was sitting in a classroom in between classes at around noon when she was attacked by the 15-year-old student.

The identity of the boy has been concealed as he is a minor.

Before anyone could intervene, the student stabbed Maheshwari repeatedly, inflicting at least five deep wounds on her face, throat and stomach. The bleeding teacher died before she could be administered medical care at the government hospital nearby. Other students, teachers and staff of the school, who rushed to the spot after hearing her loud cries, caught the boy and handed him over to the police.

After interrogation of the boy and initial inquiries, police said he was angered by the teacher scolding him and complaining to his parents about his poor academic performance. He brought the knife with him today, concealing it in a paper.

Maheshwari’s husband is the regional manager of an electronics firm, and the couple have two children.

According to Father Bosco Periyanayagam, a member of the school committee, the boy attended classes regularly but was not concentrating on his studies, which prompted Maheshwari to record her remarks in his school diary — the routine way of informing parents about their ward’s progress. Police believe this could have been the trigger for the attack, although they are continuing further investigations.