The protests, which began last week in Paris, have spread to cities including Montpellier, Nantes, Marseille, Strasbourg and Rennes. On Friday, a 17-year-old was arrested on suspicion of attempted homicide after protests in Belfort, north-eastern France, where a police officer was targeted. At least 65 staff members have been injured in the unrest, the education ministry said.
In the Paris suburb of Pantin, police charged at protesters and made arrests after projectiles were thrown at officers. Tear gas was also deployed in Strasbourg. Rubbish bins have been set on fire in Rennes and Paris.
Police have published pictures of items seized from demonstrators, including petrol bombs, an axe and mortar fireworks. "Significant damage" had been done to school facilities.
French justice minister Gerald Darmanin said things had "gone from high-school student demonstrations to a public order disturbance".
Despite the clashes, some protesters felt their actions were effective. "As far as we're concerned, we've won — our school is closed this morning," Lola, a 16-year-old protester, told AFP. She said police actions had made things worse: "It makes us even angrier — the police have no right to hit us or use tear gas on us."
The protests are driven by grievances over a lack of teachers, overcrowded classrooms and run-down buildings.