The senior student stabbed his history teacher, Alex Pammei, five times when the teacher rebuked him for consuming alcohol inside the school premises at Jawahar Navodaya Vidyalaya on Tuesday, police officials said.
The condition of Pammei is critical and currently admitted in an intensive care unit, hospital officials said.
Police have identified the accused but his name was not disclosed by the authorities.
Efforts are on to nab the student, who fled from the spot after the incident, he said.