VAULX-EN-VELIN, France » France may have just hosted its biggest outpouring of solidarity since the end of World War II in response to the terrorist attacks last week in and around Paris that left 17 dead at the satirical newspaper Charlie Hebdo and a kosher supermarket.

But in the disaffected suburbs, or banlieues, that ring France’s largest cities, those appeals for unity hardly penetrated the sense of isolation, even siege, that have left cities like this one living a parallel existence from the rest of the country.

"I am French, and I feel French," said Nabil Souidi, 23. "But here you are forbidden to say, ‘I am Charlie,’" referring to the rallying cry of solidarity since the attack on the magazine.

Souidi recently graduated from a trade school and hoped to find a job as a mechanic. Months later, he is still out of work, searching for a Plan B. "I’ll go to Syria," he said, with a sarcastic laugh in an interview over a plate of French fries and mayonnaise.

For him and many other French Muslims, the nation’s preoccupation with last week’s attacks at the hands of Islamic extremists presents a mere distraction from a fundamental social crisis that has plagued France’s immigrant neighborhoods for decades.

In numerous interviews, community leaders and Muslims and North Africans who largely populate the banlieues expressed concern that last week’s attacks in Paris would intensify an already explosive social and economic situation in the places where they live.

On Tuesday, a French association that represents 120 mayors across France issued a statement warning that the French banlieues were "on edge" amid the fallout from the attacks, and said there was an urgent need to address economic, social and educational shortfalls.

Vaulx-en-Velin, a dreary Muslim-majority suburb of Lyon, is France’s third-poorest city and representative of the problems. Many youths simply call it "a ghetto." It might also be called the Other France.

Here, and in numerous other poor suburbs that ring French cities, joblessness runs around 20 percent, about double the national average. For young people, it can be as high as 40 percent. About half of residents do not have a high school diploma. Police harassment and profiling are taken for granted as the rule.

In a time of budget cuts and austerity, conditions have only deteriorated despite years of pledges by successive governments, including President Francois Hollande’s, to improve schools and create opportunity.

The men who carried out the attacks — Saod Kouachi and his brother Cherif, who attacked Charlie Hebdo, and Amedy Coulibaly, who seized the kosher market — grew up in the French banlieues and had failed to hold down a series of menial jobs in their youth.

All were attracted to Islamic extremism by their teenage years, and many residents in the banlieues consider them bad seeds who were propelled toward the fringe.

Yet the fallout from their attacks, and the response shown by the rest of France, has been Topic A along the gritty streets of many impoverished suburbs from Paris down through the south of France.

Many worried that as Muslims, they would be lumped together with the killers. Others spoke of fears of retaliation against mosques and other Muslim symbols, as well as the specter of reprisals or even a crackdown by the police after officers were murdered in the terrorist attacks.

"People feel like there is no solution — that they are just totally divided from the rest of society," said Gounedi Traore, 37, a social worker at the Centre Social Intercommunal de la Dhuys, a community center in Clichy-sous-Bois, a suburb outside of Paris that is one of France’s most economically deprived.

"After what happened with Charlie Hebdo, I feel that this is going to set off a war," he said.

Nearly everyone agreed the fallout from the Charlie Hebdo attacks — including a heightened security response by France and its allies — is a distraction from a larger problem: a sense of increasing social and economic marginalization that many cited as a root cause of young people drifting toward extremism.

"The attacks had a global impact but not local impact," said Faouzi Hamdi, rector of the Okba Ibn Nafee Mosque in Vaulx-en-Velin.

Community leaders say France’s drawn-out economic crisis has made already scarce job opportunities even worse.

"We are not treating the problem at its roots," said Leila Legmara, a deputy mayor for education in the Paris suburb of Colombes. "Of course we need more security and resources to fight terrorism. But we also need to address what it is within our society that is capable of producing monsters."

The sense of marginalization did not disappear with the massive solidarity march across Paris on Sunday, which drew more than 1 million people and 40 presidents and prime ministers to Hollande’s side. For some banlieue residents, it seemed an almost surreal display that had nothing to do with them.

In Vaulx-en-Velin, the only Charlie reference to be seen was a sign for the Charlie Chaplin cultural center across the street from City Hall, which is topped with a drawing of a flag of its sister city, the West Bank town of Beit Sahour.

Residents there ridiculed the "I am Charlie" marches. Some said the terrorist attacks were staged. While many strongly condemned the attackers for the murders; others insisted the cartoonists got what they deserved.

Local leaders say this city of 44,000 is a microcosm of France’s failed integration policy, and the underlying social problems that have encouraged young people toward radicalization. Places like Vaulx-en-Velin have remained "priority zones" for the government since 1964, some noted.

As in Clichy-sous-Bois, youngsters here said they felt as if they were living in a separate country, detached from the social and economic benefits of the state, and abandoned by a system that preaches unity and solidarity with France’s Republican secular values.

"I totally feel cut off from France," said Karim Yahiaoui, 15, who added that he has not left this suburb more than twice in the past year.

Over the past few decades, the Muslim community in Vaulx-en-Velin has become increasingly insular. "Many people only believe their own values now, not those of the republic," said Anne Dufaud, director of the Mission, a nonprofit organization.

When Hollande led a moment of silence across France last Thursday for the victims of the attacks, two students and a teacher at a local high school, who declined to be named, said many students refused to stand.

Patrick Kahn, a manager at the International League Against Racism and Anti-Semitism in Lyon, who operates a weekly tolerance program in the schools of Vaulx-en-Velin, said simply: "The integration policy failed."

"The suburbs were left behind in government planning, so they became segregated communities," he explained. Fear of the authorities was already omnipresent, reflected in crude anti-police graffiti on many of the concrete housing complexes, which residents call "les cages de poulet," or chicken cages.

The attacks only deepened concerns about racial profiling. One woman wearing an abaya said she had left the house only twice since the Charlie Hebdo attacks because she was afraid of the authorities.

Inside schools, students said there were already deep social divisions between Muslim and non-Muslim. One community leader said it was impossible to initiate a discussion about the Charlie Hebdo attacks without first explaining satire, caricatures and freedom of expression. Teachers said their attempts at discussion had led to tense exchanges.

"Schools reflect the society," said Stéphane Gomez, general councilor and deputy mayor of Vaulx-en-Velin. Gomez is also a high school teacher in the region. "We have to talk about what has gone wrong, and reopen the debates that we’ve been afraid to talk about for so long."

In Clichy-sous-Bois, residents said such a debate would have to include a hard look at the economic and social segregation that has defined France’s banlieues decade after decade.

"We need to give people ways to succeed," said Mohamed Mokkadem, 37, who runs his own trucking company, SKL Transports.

Mokkadem had tried, to no avail, to buy a copy of the latest Charlie Hebdo that hit newsstands Wednesday. He said he was curious to see close-up the new depiction of the Prophet Muhammad on the cover.

Conditions were bleak in his neighborhood even before the killings, he said, and now, more than ever, he said, he wanted to send a pointed message to the government and the country.

"What we are asking for is to be respected according to our worth," he said. "The message, quite simply, is to be regarded as truly French."

© 2015 The New York Times Company