Protest movements have long relied on students as some of the most ardent foot soldiers. Young people have been on the front lines of protests against war, climate change and racial inequality. But in huge protests that have shaken India and France this fall, students have revolted against the failed promises of education itself.

In India, students took to the streets after the government abruptly canceled the results of a medical-school admissions exam because test questions had been leaked online. Aspiring doctors had to take the test again, after many spent years studying for up to 12 hours a day in hopes of winning one of the coveted spots — and the chance of upward mobility. Young people across the country saw the scandal as emblematic of a broken education system and were furious.

In France, students in poor suburbs outside Paris began protesting the decrepit physical condition of their schools, an opaque university admissions system and absent teachers. French education had long promised to serve as a “social elevator” enabling young people to advance in society, but had fallen into disrepair. Soon, demonstrations spread across the country and, in some cities, spiraled into rioting.

In both countries, the anger of the students shows no signs of abating. And while in many ways France and India could hardly be more different, their unrest was sparked by a similar source of outrage: the breakdown of a foundational social contract that one could call the meritocratic bargain.

It is a promise that lies at the core of many countries’ political compacts. Though specifics can vary, the central proposition usually goes something like this: A fair society rewards merit. Educational achievements are a good measure of merit because education is open to all and leads to valuable skills. Therefore, education should be a route to social and economic advancement.

The value of this system is not just that it selects for those with high ability, but also that it offers a justification for the resulting socioeconomic hierarchy — including who ends up at the bottom. “All selection mechanisms generate losers,” said Nicholas Kuipers, a professor at Princeton University who studies the politics of meritocracy. “The question is, Who do you want to be a loser, and who do you want to be a winner?”

In many places around the world, that system has proved to be remarkably effective, in large part because education has translated relatively straightforwardly into economic mobility.

But increasingly, many who work hard at higher education, often going into debt and sacrificing years of earnings potential to do so, are finding that the rewards are not there at the end. Instead of expected winnings, many young people are greeted with a life of economic struggle.

This discontent is affecting politics elsewhere as well. In the United States, data from The New York Times showed that 70 percent of voters under 30 in the recent midterm elections cast their ballots for Democrats, who tapped educated young people’s widespread frustration over being saddled with debt and stuck in low-paid, dead-end jobs.

In Serbia, student protests grew into a political movement that ousted Aleksandar Vucic, the country’s longtime nationalist strongman, in an election last month. And young people across Europe are set to walk out on Nov. 20 in a general strike that could disrupt schools and businesses throughout the continent.

An even bigger threat looms on the horizon, one that could upend the bargain everywhere: A.I. promises to dramatically restructure, or perhaps sever completely, the relationship between education and well-paid work.

That has the potential to further challenge not only the distribution of economic rewards, but the political bargain on which modern societies have been built.

Historically, such moments have been explosive — even revolutionary.

Meritocracy’s Promises and Pitfalls

The version of the meritocratic bargain we see today, with university education as a primary filter for middle-class careers, is a relatively recent construct, and not to be taken for granted.

Britain didn’t introduce universal, free secondary education until 1944. In the United States, college was largely the province of the privileged few until the G.I. Bill opened access to veterans after World War II. Around the same time, the SAT created the first nationally standardized benchmark for admissions.

In countries whose economies developed later, the bargain took even longer to take shape. In India, the national college entrance exam was not introduced until the 1960s. In China, there is a long history of using meritocratic exams to select civil servants and other elites, but that system was disrupted by 20th-century reforms and the Cultural Revolution. The modern system was ushered in by Deng Xiaoping. In 1977 he re-established the national “gaokao” exam system as part of a post-Cultural Revolution rebuilding process. In the late 1990s, further reforms radically expanded university access.

For individuals, this access to education promised more money, more status or both. But for governments, it also offered political stability — a way to convince people to buy into society as currently structured, by promising the potential for advancement to the underprivileged without ousting those who had wealth and power already.

Research has shown that the prospect of upward mobility — sometimes abbreviated as POUM — can make the poor less likely to demand redistribution. In China, merit-based selection for civil service jobs made people more willing to tolerate inequality, Hanzhang Liu, a political scientist at Florida State University, has found.

When people believed the system was meritocratic, they were more likely to attribute their failures to their own poor abilities, or to the high quality of the competition, she said. But when they did not believe so, those who lost out on jobs were more likely to consider the system rigged.

Still, education-based meritocracy puts significant burdens on the young people working to advance, and on their families. In India, students often go into debt and spend years of grueling study to try to win spots at the most prestigious engineering and medical programs.

In South Korea, national tests have generated an entire industry of cram schools known as hagwons, where students toil for hours each day on top of their regular schoolwork. In the United States, networks of charter schools like KIPP popularized the idea that for poor, ambitious kids, “college starts in kindergarten.” And when actual college starts, American students can easily take on six-figure debts for their degrees.

The Danger of Shattered Expectations

Just as the meritocratic bargain can be a source of social cohesion, a breakdown can become a trigger for social explosion.

In 1905, China abolished the national civil service exam that had for 1,300 years been a major way to recruit elites, including government bureaucrats. That move came as a shock to the people who had invested in years of education, hoping to earn a privileged position in society.

Those shattered expectations contributed to the revolutionary uprisings that eventually overthrew the imperial dynasty in 1911, according to the economists Ying Bai, at the University of Hong Kong, and Ruixue Jia, at the University of California, San Diego.

In an influential 2016 paper, they found that frustrated commoners who had hoped to become elites via the exam were especially likely to join the revolution. Disillusioned scholars flocked to revolutionary organizations in search of alternative routes to advancement, and became a major force behind the revolt.

That is not to say that France’s unrest signals the imminent return of the guillotine. But the recent protests there, and in other European countries like Italy and Spain, were fueled, in part, by the sense that the old order was enriching itself at the expense of providing opportunities for young people.

Much the same can be said of the student protest movement that led to the election defeat of Mr. Vucic in Serbia, where angry young people felt that meritocratic opportunity had been crowded out by corruption.

Protests can be a blunt instrument. But data show that the demonstrators have a point. In Europe, high unemployment rates for young people, paired with skyrocketing costs of living, have put the traditional milestones of independent adulthood out of reach for many.

Even in countries with healthier economies, there are signs that the breakdown of the meritocratic bargain is already having political consequences. In India, economic growth has been stronger, but it has not created enough jobs to keep up with the expansion of higher education.

In the United States, the emphasis on higher education as a sorting mechanism has led to people pouring tens of thousands of dollars into degrees that no longer necessarily confer economic advancement but still charge as if they do. Discontent has fueled the rise of political movements like the Democratic Socialists of America and efforts to unionize the work forces of companies like Starbucks and Amazon, Noam Scheiber, a Times labor reporter, writes in his new book, “Mutiny: The Rise and Revolt of the College-Educated Working Class.”

But the biggest blow to the meritocratic bargain may be yet to come, as many fear that A.I. could do for knowledge work what a meteor strike once did for the dinosaurs.

A.I.’s arrival has already wiped out some entry-level technical jobs. In the United States, young coders are finding themselves working at Chipotle rather than starting the highly paid tech careers they had expected.

Even if A.I. does not eliminate professionals like lawyers, scientists and doctors, it may radically reshape those fields — and perhaps slash the salaries that come with them.

Some professions may adapt by making greater use of A.I. tools, even as other careers see their pay and numbers collapse. With time, new educational structures may also develop to match skills and meritocratic selection to the demands of a new economy.

But such profound economic change is by its very nature disruptive. In the meantime, it is likely to sow even more confusion about how young people can set themselves up for success, or prevent themselves from sliding down the economic ladder.