Montreal police say the incident occurred at about 10 a.m. today at John F. Kennedy High School in the city’s north-end St-Michel neighbourhood
They say the suspect, who is believed to be a student, was arrested near the school and was being taken to a detention centre for questioning.
The teacher, a man in his 40s, was taken to hospital with superficial injuries that are not life-threatening.
Police spokesman Jean-Pierre Brabant says the school was briefly locked down while police tracked down the suspect, but that order has since been lifted.
He says it’s still too early to know what charges the suspect could face.