A 14-year-old who stabbed his art teacher told French police he attacked her because he had "too much hatred", a prosecutor has said.

The 60-year-old woman's condition remains a "serious concern" after she was stabbed three to four times in her chest in front of 22 students in south-eastern France on Tuesday, a local official said.

Toulon prosecutor Raphaël Balland said in a statement that the boy had premeditated the attack, having described to police taking the knife from his kitchen at home with the "intention of stabbing his teacher".

La Guicharde school, in Sanary-sur-Mer, was evacuated after the attack on Tuesday, and lessons the next day were cancelled.

Balland said there was no known religious or political motivation for the stabbing and that the student was allegedly upset that the teacher had reported several disciplinary incidents against him, which the boy said were "unfair".

The teenager told authorities he "deeply regretted" the attack, AFP news agency reported, and felt more hatred towards himself than the victim.

A decision on whether to place him in pre-trial detention will be made when he appears in court.

The victim, who has been at the school for 28 years, according to AFP, is in Sainte-Anne Military Hospital in Toulon. She is reported to have been stabilised after surgery but remains in a serious condition.

It is the latest in a series of attacks by students in French schools in recent years.

Last year, a 14-year-old was charged with the murder of a teaching assistant after allegedly stabbing her to death in June.

In a separate case in April, a student killed a girl and wounded several others in a knife attack in the western city of Nantes.

In 2020, teacher Samuel Paty was murdered by a Chechen refugee outside the school where he taught in a suburb of Paris, an attack which was motivated by religious extremism.

Education minister Édouard Geffray, who visited the Toulon school on Tuesday, has described the attack as "unacceptable" and said that since March last year, 525 bladed weapons had been seized at schools "before they could cause injury".

"Schools reflect our society, and they cannot, on their own, stem the rise in verbal and physical violence that characterises our times," he wrote on X.

"The real challenge lies here: fundamental work to de-escalate tensions. This involves families, teaching staff, elected officials, and every citizen. This is a fight we must wage together."