Tear gas clouded the streets in the eastern city of Strasbourg, fireworks were aimed at police lines in Marseille in the south and rubbish bins set ablaze in Rennes in the west. In Paris, where there were also skirmishes, students waved placards reading "We have a future to build, not to endure".
In addition, the government says that around 300 police and firefighters have been treated for injuries, and some 2,000 people – mainly minors – taken into custody. For their part, student groups say they have a long list of people injured by police. Two teenagers have serious eye injuries and one has lost many of his teeth.
The problem would be hard enough if it was just a question of meeting the protesters' demands. But there is another dimension – a political and social one – which makes this student crisis far more dangerous than in the past.
The demands do exist, even if they remain vague. They are about money – the lack of it – and the need for more teachers, smaller classes and better buildings.
On such matters, many in France would agree with the teenagers. Certainly using protest to demand money from government is such a national habit that even governments agree it's legitimate. And of course, things are indeed getting worse in the education system – because money is so tight.
The protests have spread across France, and some university students are now joining in
This week Prime Minister Sébastien Lecornu published his draft for next year's budget. The motif is "More cuts – and this time we're serious!"Whether or not he manages to remove €54bn (£46bn) from state spending, as he promises, remains open to question.
But it is surely obvious that the era of public largesse to defuse social unrest in France is now in its twilight. Students demanding an extra school nurse or insulation in the dining-block are likely to be disappointed.
The far greater fear is that these student protests are being manipulated by the hard left – and that the violence of recent days is a foretaste of what awaits a dangerously polarised society in the year of elections that is coming.
For the right and centre, there is no doubt that behind the student trouble lies the cunning hand of the France Unbowed party (LFI) and its popular presidential candidate, Jean-Luc Mélenchon.
LFI leaders have regularly appeared next to the students – notably in the Paris suburb of Saint-Denis whose mayor Bally Bagayoko was criticised for saying that "violence can sometimes be legitimate."
Bally Bagayoko (left) and presidential candidater Jean-Luc Mélenchon (right) have supported the right of the students to protest
An internal report prepared for the Paris police department which was leaked to the media analysed the opening of the movement in Seine-Saint-Denis. It concluded that students were being "egged on by far-left elements from students unions… and political groups such as… LFI."
It said the tensions "could be part of a flame-kindling strategy… aimed at imposing their ideas ahead of the national elections".
In support of its conclusion, the report's writers cited the presence of protesters who are not themselves lycéens, the vagueness of the demands, the flying of Palestinian and Algerian flags, and the use of tactics – like calling for supplementary protests at police-stations - that come from the radical-left playbook.
The LFI strongly denies doing anything more than lending its natural support to a movement it regards as legitimate. On Thursday Mélenchon called on students to avoid violence "which only serves our enemies' interests".
But his opponents believe that the 75-year-old veteran – who stands a good chance of making it to the second round of the presidential elections in May, probably against the hard-right's Marine Le Pen – knows exactly what he is doing.
Polls show he has massive support – some 40% -- among 18-24 year-olds in France, and that this is concentrated in the populous, high-immigration city suburbs where his talk of a "new France" and "creolisation", to reflect France's changing language and population, are highly appreciated.
But young people are also the biggest abstainers in French elections, so the strategy – as the elections approach – will be to give constant reminders to this part of the population that the LFI is at their side, and that their vote can count.
Whether this will be enough to ensure victory for Mélenchon is another matter. He must surely take seriously the polls which all show him losing massively in a run-off against Le Pen.
If that happens, France will be in very unstable territory - for which the young people's protests of recent days will indeed have been a harbinger.
Six months before next year's presidential election, opinion polls consistently show the deep unpopularity of Macron and his centre-right-leaning government. Planned budget cuts, which exacerbate the funding crisis in education, have fuelled the discontent
The protests erupted in the Paris region last week but have turned increasingly violent as they spread nationwide.
Justice Minister Gerald Darmanin told RTL radio that police had arrested 2,000 people, most of them teenagers, since the protests began. He said that parents of those inflicting damage to property should be made to pay reparations.
400 high schools — roughly one in 10 — were closed on Friday due to the unrest and Education Minister Edouard Geffray urged parents to dissuade their children from protesting in the streets. "In the streets, the children are in danger," Geffray told BFM TV.
Several students in the Paris region whom Reuters spoke to outside high schools earlier in the week said they were staying away from the protests on Friday due to the escalating violence.
Darmanin said the student protest movement had been hijacked by "outsiders".
Students blockading their high schools have voiced anger over overcrowding in classrooms, regular shortages of teachers and dilapidated buildings, blaming years of underinvestment.
"We are 35 per class, we don’t have enough chairs in classrooms, the one hour lunch break (is too short) for everyone to get food,” 15-year-old Kesia told Reuters in the Paris suburb of Pantin before running off as the police used tear gas.
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Under the draft 2027 budget presented by the government on Thursday, the education budget is set to increase by a below-inflation 1.7% to €65.53 billion, excluding teacher pensions.
Education is traditionally the largest budget item, but that changes next year with debt servicing costs expected to reach €74.5 billion, according to the draft bill.
Intelligence agencies told a crisis meeting on Thursday that the protest movement had been initiated by politicians from the hard-left France Unbowed party (LFI). Senior LFI lawmakers rebutted the allegations and accused the government of politicising the protests ahead of the election to replace Macron.
Students and rights groups have accused the police of using heavy-handed tactics against minors, including the use of batons, tear gas and non-lethal flash-ball guns.
Amnesty International cautioned against the excessive use of police force. "Students must be protected, not beaten with batons," the advocacy group said on social media platform X.
The interior ministry on Friday said that they had opened three investigations into police violence against protesters.
In a sign the protests may spread beyond French borders, some high school students in the city of Liège, in Belgium, began protesting on Thursday. A city hall spokesperson said high schools were closed on Friday.