The alleged attacker was arrested at the scene after being restrained by a member of the teaching staff.
ADVERTISEMENTAt least one person has been killed and three others wounded in a stabbing attack at a high school in the western French city of Nantes, police say.
The 15-year-old suspect stabbed four people with a knife during a lunch break at the private Catholic Notre-Dame-de-Toutes-Aides High School, a national police official said.
Teachers subdued him and he was later arrested by police, the official said.
The motive for the stabbing is unclear.
The suspect had sent an email with unspecified grievances to all students just before the attack, students at the school told French media at the scene.
One of the targeted students died of their wounds.
Three others were wounded, including one who was hospitalised in "very serious condition," Nantes Mayor Johanna Rolland told reporters.
She did not give details about the suspect, but raised concerns about ″the mental health of the youth of this country."
Such fatal attacks are quite rare in French schools.
France's Prime Minister François Bayrou ordered tighter security inside and outside schools nationwide and called for new proposals within four weeks for preventing and punishing knife violence by teens and children.
He said metal detectors at schools could be considered.
Interior Minister Bruno Retailleau said the attack was "probably" an isolated act, without providing details about the investigation.
The school confined the students inside for hours while police secured the site and carried out questioning, according to French media.
Police and armed military forces surrounded the area and worried parents waited outside the perimeter.
French President Emmanuel Macron praised the courage of the teachers who intervened, saying in a post on X that they "undoubtedly prevented other dramas."
ADVERTISEMENTAn official at the school, which is part of a complex housing a primary and middle school, would not comment on what happened, saying the school is concentrating on caring for the students who were on campus at the time.
The school website was also down.
"A terrible drama happened at midday today and my thoughts go first to the teenage girl who lost her life and to the three wounded students" and their families, Education Minister Elisabeth Borne said.
The teachers "are in shock, and at the same time, very mobilized to return to class."
ADVERTISEMENTFrance's counterterrorism prosecutor's office said it was ‘"evaluating" the incident, but did not take over the investigation as it does when terrorist motives are suspected.
Counterterrorism agencies across Europe and beyond have warned recently about a new generation of underage attackers or plotters who have fed on ultraviolent and potentially radicalising content online.