High school pupils shout slogans while taking part in a nationwide day of protest against deeply unpopular labor reforms that have divided the Socialist government and raised hackles in a country accustomed to iron-clad job security, on March 9, 2016 in Bordeaux, southwestern France | Nicolas tucat/AFP/Getty Hollande’s labor reform infuriates French youth For the first time, French students rally against a left-wing government.

PARIS — France's reform-killers are out.

François Hollande faced a wave of youth outrage Wednesday over controversial plans to overhaul France's labor system, as tens of thousands of students took to the streets to call for a bill's withdrawal.

High school students ditched class and barricaded an estimated 90 establishments before joining university peers for mass rallies against the labor reform bill in Paris, Bordeaux, Marseille, Toulouse and other cities.

At the same time, train conductors went on strike over labor conditions in their sector, causing disturbances to train traffic in the larger Paris region. In many places trade union members joined up with students to protest the so-called "El Khomri" labor reform bill, a far-reaching text that would help firms get around the 35-hour work week, limit severance payouts and reduce unions' power to block company moves.

The combined movement is a serious challenge to Hollande's authority, his will to reform and his chances of ever getting re-elected — probably the biggest one he has faced in four years of being president.

It's also a historical first: Never before have students launched a major protest movement against a left-wing government. When they have directed their ire in the past against right-wing governments, students have been remarkably effective in knocking down reforms — to the extent that it's made generations of French leaders allergic to the risk.

From the student protests of May 1968, which ushered in a wave of social reform, to a 2006 movement against youth job contracts that forced the government to withdraw its bill, young people have prevailed against the establishment, time and again.

This time, the movement is as much against a reform bill on which they say they were never consulted, as it against a president whom many feel has betrayed left-wing values.

"When I voted Socialist, I expected nothing. I'm still disappointed," read one sign carried by a group of students marching toward Paris' Place de la République.

The reformer

Deeply unpopular and likely to lose a bid for re-election in 2017, Hollande is trying to prove his mettle as a reformer in a country famously resistant to change.

While fighting against the left-wing of his Socialist party over a controversial plan to strip convicted terrorists of their French nationality, he doubled down earlier this year by launching the labor reform — a measure the European Commission considers long overdue, and one which economists say may finally jump-start hiring in France's moribund economy.

Hollande and his prime minister, Manuel Valls, were equipped to battle a political insurgency over the former measure. But they appear to be unprepared for the scale of protest — in the streets, in media and online — against their labor bill.

Days after a draft text of the bill was published, an online petition against it went viral. It has now been "signed" by more than 1.2 million people.

All major trade unions, including the reform-minded CFDT, have criticized the bill, and hardline groups like SUD and CGT vow to carry on protesting until it is buried and forgotten.

Efforts by Hollande and Valls to head off the wave of outrage have been clumsy, and at times laughable. In order to inform the public on the 120-page bill, the government launched a Twitter profile named "The Labor Law" that personifies it. ("Hello Twitter, I am the #LaborLaw bill. A lot said is said about me, but not much is known. How about we get to know each other better?" reads the profile.)

Mocking replies along the lines of, "How about we help you throw your law into the trash?" are typical.

In trying to adjust their position on the law, the government has vacillated between toughness and conciliation.

After first hinting that Valls could use a special 49-3 decree to force the bill through parliament, the government has backtracked on that course of action and announced a two-week delay before sending it to parliament for "consultations" with trade unions.

Labor Minister Myriam El Khomri says the government will consider "adjusting" the bill to take into account some of the grievances.

But the protest movement has just begun. If it keeps growing, the pressure on Hollande to back down and save the Left from implosion could become unbearable.

In that case Valls, who has pledged to stay with it, may find his position in the government untenable.