America's success has long depended on the success of immigrant families. Just this month the Census Bureau reported that one in five Americans were either born in a foreign country or have a parent who was. And some of these immigrant families are soaring as never before: Urban school honor rolls swell with immigrant children; immigrant adults wield unprecedented power in universities, government, and business; immigrants own 40 percent of technology companies in Silicon Valley.

That's the bright side of the story. The dark side is quite shocking: The longer immigrant children live in this country, the worse, on average, their health, their attitude, and their school performance. What's more, with each subsequent generation, immigrant children do worse and worse. On average, first-generation children function at significantly higher levels than do typical American-born children. But, by the third generation, that advantage is gone. To take just one example, the school performance of first-generation Chinese teenagers—one of the highest performing immigrant groups—markedly exceeds white teens. By the third generation, the difference disappears: English proficiency and school performance are inversely related. In other words, while once upon a time people came to the United States expecting to make better lives for their children, today the sad fact is that the more Americanized immigrant children become, the less successful they are.

The most obvious cause of this slide is that classic villain: children's peer groups. "[H]anging out with ... peers who value socializing over academics," as Temple University's Laurence Steinberg puts it in his 1996 book Beyond the Classroom, causes immigrant children over time to "resemble the typical American teenager, and part of this package of traits is, unfortunately, academic indifference, or even disengagement." Peer influences, Steinberg and others argue, also drive immigrant teens to crime, drug abuse, and depression. With each subsequent generation, this argument goes, immigrant children spend less time with other immigrant children and more time with Americanized ones and, therefore, feel negative peer influences more and more strongly.

This story has some truth to it. Immigrant children pick up American youth culture very quickly. Marcelo and Carola Suarez-Orozco, Harvard researchers conducting a major study of immigrant children, observe that newly arrived immigrant children "talk about how beautiful school is and how wonderful the principal is." What do they say a few years later? "`School's boring and the principal is an idiot.'" As a former Boston school principal put it: "As soon as these sweet, respectful immigrant kids arrived, my whole staff would get this sinking feeling. We'd see exactly where these kids were heading, that pretty soon they'd have all the attitude of American kids."

But peer influences only explain so much. For one thing, peer influences are exceedingly complex and variable. Some are even positive: There is strong evidence that some peer groups influence children to stay in school and eschew drugs. Where peer groups do have a negative influence, the problem is often hopelessness: Research indicates that negative peer groups most often breed when children feel hopeless about their future as adults. What's more, negative peer groups have been around for as long as there have been immigrants--destructive teen gangs have existed in American cities since the late 1700s, and cracking on school and adults (remember Huck Finn and Tom Sawyer) has always marked American youth culture. But in the past, these negative peer groups notwithstanding, the performance of immigrant children didn't deteriorate the longer they stayed in the country, and succeeding generations didn't do worse than the ones before them.

A better explanation for the decline in immigrant children's fortunes lies in a relationship even more defining than their relationship with their peers: their relationship with their parents. The more mature children are, the less likely they are to be negatively influenced by their peers. Mature children have a steady internal compass—a self that exists outside the particular impulses of their peers. And psychologists generally agree that the broad foundations of childrens' maturity come from their parents. Children need caretakers who communicate hope about their future; transmit important social and moral expectations; regularly listen to and understand them; and reflect back their understanding. Just as important is being esteemed by a caretaker who a child, in turn, respects and esteems. The psychoanalyst Heinz Kohut argues that, in adolescence especially, children mature by receiving the ongoing attention of adults who are not only esteemed but idealized.

Americanization erodes these critical aspects of parenting. Consider first-generation children and their parents. As the rates of single parenthood and maternal employment have increased in the last few decades, the time and energy parents have to focus on their children has declined. First-generation children today are far more likely than their counterparts of 50 years ago to be scraping for crumbs of time from a single parent who not only works but is frayed from ricocheting among two or three jobs. And, while research suggests that children in single-parent homes tend to fare as well as children from two-parent families if their parents are buoyed by relatives and neighbors who provide support, over time first-generation immigrant families tend to drift from relatives and tight-knit immigrant communities into more anonymous neighborhoods where that support is lacking.

People don't usually think of immigrants as single parents. But, because parents and children often arrive in this country at different times, many children are separated from their parents in the immigration process. In the Suarez-Orozco study, 85 percent of children were separated from at least one parent for extended periods of time; 49 percent were separated from both. Rates of family separation might have been as high in other eras; it's hard to know based on existing data. But what is clear is that these days children are more likely to be separated from their primary caretakers—their mothers—who are increasingly drawn to the United States by the high demand for service workers. (In the past, men usually came to the United States first, drawn by industrial or agricultural work.) The Suarez-Orozco study found that 55 percent of immigrant children were separated from their mothers during the migration process.

And even when parents are reunited with their children, it's often hard for parents to retain their high regard. American teenagers famously view their parents as out of touch with mainstream American culture—try naming a contemporary teen movie in which parents are not cartooned as disconnected dolts. But for new immigrant kids, the problem goes far deeper. First-generation children often don't respect their parents' values, and they view their parents as obstacles to forming an American identity. "[Vietnamese] parents are in, but not of, America," writes Min Zhou, a UCLA professor studying Vietnamese immigrant children, and their children "struggle to find answers to a set of difficult questions: 'Why do my parents object to my acting like other American kids? ... How can I fit in with my friends without offending my family? Can I ever grow up as an American in a Vietnamese family?'"

To be sure, these kinds of intergenerational troubles in immigrant families are not new; but they are exacerbated by the fact that so many families now arrive from culturally dissonant Asian and Latin American countries rather than European ones. Immigrant parents who embrace values such as collective responsibility and unquestioning deference to authority—prized in many Asian and Latin societies—can become increasingly alien to children embracing American notions of individualism and egalitarianism. Zhou observes that in Vietnam the self is not thought to exist apart from one's family.

At the same time, this cultural dissonance undermines traditional methods of parental discipline, a critical means of maintaining respect. The more that first-generation children are exposed to relatively permissive American families, the more they bridle at their own families' moral standards, causing deep parent-child ruptures. And some parents blame the government for literally tying their hands. I conducted a focus group with Vietnamese parents in Boston who fear that government social service agencies will take away their children if they hit them in any way. I've heard similar concerns from Haitian, Dominican, and Jamaican parents: The United States should not tolerate corporal punishment, but social service bureaucracies need to find a way to help these families replace disciplinary methods they've been using for hundreds of years.

But something else undermines the respect that first-generation children feel for their immigrant parents even more: the low-status service jobs in which those parents are often stuck. Perhaps more than ever before, children today are saturated not only with images that wildly glamorize wealth and fame, but that also degrade many common forms of work. It has become routine in schools to motivate drifting students by direly predicting that if they don't study they will end up "flipping burgers at McDonald's." The problem is that many immigrant parents are flipping burgers, or cleaning houses, or driving cabs. "A lot of immigrant kids see what their parents do for work and think their parents are chumps," says Mary Waters, a Harvard sociologist studying immigration. Even worse, it's an assessment that over time many immigrant parents come to share. "When many immigrant parents first get here they think that they have good jobs, that they're making a lot of money," adds Waters. "But soon they realize that they're not making much at all compared to other Americans. They feel like they've been had."

These changes in the way parents feel about themselves may also be key to understanding why second- and third-generation children fare worse than first-generation children. Many first-generation parents retain high hopes for their children even when they lose hope for themselves—that's why they work themselves to the bone. But as many of these children find themselves in the same low-status or menial jobs that dragged down their parents—immigration researchers now speak of a "rainbow underclass"—this kind of hope, too, may slip away. "What declines with each generation," says Carola Suarez-Orozco, "is parents' optimism, their belief in their children's futures." Children with hope can withstand a great deal; children without it are vulnerable to every adversity.

The forces that undermine immigrant families, then, are the same ones that undermine other poor and working-class American families: the awful choice between making a reasonable living and spending a reasonable amount of time with their children—and the self-destructive behavior of children who see themselves trapped in multigenerational cycles of poverty and despair. Conservative commentators often hold up immigrants as evidence that economic hardship doesn't represent a daunting obstacle to success in the United States. Look at immigrants, they say, who overcome dead-end jobs and crummy neighborhoods and move into the middle class because of their strong families and strong values. But new research makes emphatically clear that those jobs and those neighborhoods undermine those families and those values; far from proving the irrelevance of economic forces in circumscribing upward mobility, immigrants dramatically testify to its power. In that way, as in so many others, America's immigrants are just like everyone else.