French officials say the incident happened in the French town of Grasse
At least one student armed with several weapons has attacked a high school in the French town of Grasse.
The government has sent a nationwide terrorist attack warning to smartphones, and police urged local residents to stay indoors.
France's interior ministry says at least three people were hurt after the shooting at the Alexis de Tocqueville high school.
Police sources say a 17-year-old student has been arrested, and the suspect was carrying a rifle, two handguns and two grenades.
Police say there is no reason to believe there was a terrorist motivation behind the incident.
The French Education Minister said the shooting appeared to be an act of "madness" by someone fascinated by firearms.
Two pupils were among those hurt, and the headmaster was also injured when they attempted to intervene.
Reports had initially suggested there was a second suspect on the run, but according to TheLocal.fr police have since indicated there was only one shooter involved.
Students who witnessed the shooting said they took cover under the tables after hearing a bang.
One told France Inter radio: "I went to close the windows and saw a guy who looked at me in the eyes. He seemed to be a student and not very big. He shot in the air and ran away."
A shopkeeper opposite the school told Franceinfo he heard "several shots" and three schoolgirls had taken refuge inside his store.
Other schools across the town were put on lockdown following the incident, but that order has since been lifted.
France remains in a state of emergency following deadly attacks in Paris and Nice over the past two years.