Fires have broken out at several schools in France, as student protests by blockading education institutions nationwide over school funding and studying conditions.
Blazes were reported at two high schools in Nantes, western France, while another was filmed engulfing the entrance to another in the northern city of Rouen.
Students are protesting about a lack of teachers and staff, overcrowded classrooms and run-down buildings. University students joined the demonstrations on Thursday, citing similar demands.
Prime Minister Sébastien Lecornu held a crisis meeting on Thursday to discuss the unrest. The government said afterwards that the student-led demonstrations had descended into "urban violence".
Both fires in Nantes spread after a bin was set alight. The blaze at the Nelson Mandela high school, in the city centre, then spread to the front of the building, damaging the entrance hall.
In the southern city of Marseille, staff at Victor Hugo high school were splashed with petrol as protesters reportedly filled containers.
While in the north, a headteacher at Degrugillier high school, in the village of Auchel, was injured in the ear by a wayward firework.
The blockades and protests at French lycées - for 15-18 year olds and equivalent to sixth forms in the UK or high schools in the US - began last week before spreading to hundreds of schools across the country.
French media report 625 people were arrested on Wednesday alone while 83 police officers were injured. More than 600 arrests had been made by midday on Thursday, excluding Paris, broadcaster ICI reports.
At least 30 universities have also reportedly been blockaded, including campuses in Rennes and Paris.
On Thursday, public transport services in Marseille and Strasbourg were halted due vandalism, threats of violence and to hinder protesters from moving around.
Seventeen-year-old Raphael took part in protests outside a school in Strasbourg, where barriers were used to obstruct nearby tram tracks.
He voiced his frustration at his school's facilities in an interview with news agency AFP, saying some rooms had leaks and that there were not enough toilets.
"The building is falling apart, the cafeteria is too small. There's zero budget, zero resources, not enough supervisors," Raphael said.
While France's next general election is still months away, the protests and how French authorities are responding to them has been heavily politicised.
The government and hard-right politicians have blamed the hard left for igniting protests, which are being organised by a union representing lycée students.
Bally Bagayoko, the mayor of a Parisian suburb and member of the radical left La France Insoumise (LFI) party defended earlier remarks in which he said violence could be legitimate in some cases - referencing cases in which protesters had allegedly been shot at while not wearing helmets or bulletproof vests.
LFI leader and presidential candidate Jean-Luc Mélenchon, meanwhile, stressed he was in favour of non-violent protests, while arguing that blaming the left would not solve the issues motivating the demonstrations.
Earlier, leader of the hard-right National Rally Marine Le Pen said: "This is no longer about high school student protests. It is about riots organized by professionals and overseen by deputies from La France Insoumise."
The presidential candidate called for a new anti-rioting law to be passed.
Left-wing mayor of Marseille Benoît Payan condemned the "unacceptable violence" in his city.
While young people were "legitimately concerned" about their future and public services, they must express themselves in a calm fashion, he said.
Eric Ciotti, the Republicans mayor of Nice, said the parents of those found to have damaged school property should be made to pay for the repairs.
