- The teacher is being interviewed again to determine why he fabricated the story
- He is hospitalized with non-life-threatening wounds
But in an interview later at the hospital, the man admitted to making up the story, the Paris prosecutor told CNN.
Earlier, the male teacher told authorities that a masked man had stabbed him in the throat and abdomen while shouting that the attack "was for Daesh," according to the French newspaper Le Parisien.
Daesh is one of the names widely used for ISIS, or the Islamic State.
The teacher is hospitalized with non-life-threatening injuries, officials said. It's not clear how he was injured.
He's being interviewed again to determine why he claimed he was attacked, Le Monde reported.
The man, 45, has been teaching at the school in Aubervilliers for 20 years, Mayor Pascal Beaudet said, according to Le Parisien. Beaudet noted earlier -- before the man admitted fabricating the story -- that the school guard said he did not see an attacker.
Security was tightened at French schools in the wake of the November 13 terror attacks in and around Paris that left 130 people dead.
France on alert
France is still under a state of emergency, so the initial report that the teacher had been assaulted prompted a swift response in a metropolitan area still on edge after last month's massacre.
ISIS claimed responsibility for those attacks. In response, President Francois Hollande vowed to destroy the terror group and intensified an international military campaign against ISIS territory in Syria and Iraq, sending French warplanes to pound ISIS targets in the terror group's northern Syrian stronghold of Raqqa.