The teacher was stabbed in the side and throat while preparing for his class on Monday at a school in Aubervilliers, northeast of Paris, but his life was not in danger, a police source said.
The attacker was dressed in painter's overalls and a balaclava and arrived without a weapon but grabbed what appeared to be a box cutter that was lying in the classroom. According to local prosecutors the man shouted: "This is Daesh. This is a warning."
Daesh is another name for IS.
The brief exchange was reported by a witness working inside the school. The attacker fled after stabbing the teacher and the probe has been taken over by anti-terrorist investigators.
The attack comes as Paris is on high alert after a wave of shootings and suicide bombings at Paris nightspots on November 13 that killed 130 people and left 350 injured.
Security has also been boosted at schools.

