LOS ANGELES

THE alleged involvement of two ethnic Chechen brothers in the deadly attack at the Boston Marathon last week should prompt Americans to reflect on whether we do an adequate job assimilating immigrants who arrive in the United States as children or teenagers.

In 1997, we started a large-scale study of newly arrived immigrants, ages 9 to 14, in 20 public middle and high schools in Boston, Cambridge, Mass., and the San Francisco Bay Area. Our participants came from Asia, Latin America and the Caribbean; many fled not only poverty but also strife, in countries like Guatemala, Nicaragua, El Salvador and Haiti. Over five years, we interviewed more than 400 students, as well as their siblings, parents and teachers. We gathered academic records, test scores and measures of psychological well-being.

The two brothers accused in the Boston bombings — Tamerlan Tsarnaev, 26, who was killed on Friday, and his brother, Dzhokhar, 19, who was captured later that day — were around 15 and 8, respectively, when they immigrated. Both attended Cambridge Rindge and Latin, that city’s only public high school. They were not part of our study, but they fit the demographic profile of the subjects of our research: birth to families displaced by war or strife, multiple-stage (including back-and-forth) migration, language difficulties and entry into harsh urban environments where gangs and crime are temptations.

When asked “what do you like most about being here?” an 11-year-old Haitian boy in Cambridge told us, “There is less killing here.” His response was notably succinct, but not unique.

A Salvadoran 10-year-old whose family had narrowly escaped death squads recounted intense loneliness. When a firecracker was set off in his working-class Cambridge neighborhood, he plunged into the arms of a stunned researcher.

A 12-year-old girl whose family had fled chaos in Guatemala for the Bay Area similarly turned inward. She lamented being “encerrada” (locked in) because of gang violence in her new community.

Not surprisingly, students from strife-torn areas were more likely than others to report psychological symptoms like anxiety, depression and trouble concentrating and sleeping.

Many newcomer students attend tough urban schools that lack solidarity and cohesion. In too many we found no sense of shared purpose, but rather a student body divided by race and ethnicity, between immigrants and the native born, between newcomers and more acculturated immigrants. Only 6 percent of the participants could name a teacher as someone they would go to with a problem; just 3 percent could identify a teacher who was proud of them.

When asked what Americans thought about immigrants of their national origin, 65 percent of the students provided negative adjectives. “Most Americans think we are lazy, gangsters, drug addicts, that only come to take their jobs away,” a 14-year-old boy in the Bay Area told us. We also found that many educators, already overwhelmed by the challenges of inner-city teaching, considered immigrant parents uninformed and uninvolved.

Having just one friend who spoke English fluently was a strong predictor of positive academic outcomes. Yet more than a third of the students in our study reported that they had little or no opportunity even to interact with native-born students, much less make close friends.

Our research also confirmed that kids who arrive during their high school years, as Tamerlan Tsarnaev did, face bad odds, especially if they experienced interrupted schooling, family instability and traumatic dislocations back home.

According to news accounts, the younger brother, Dzhokhar, was a “smart” and “respected” student at Rindge and Latin, where he had friends and was a wrestling-team captain. But at the University of Massachusetts, Dartmouth, he was flunking out. The sociologistAlejandro Portes of Princeton and the educational psychologist Cynthia Garcia Coll of Brown have found declining performance over time. Nearly two-thirds of the students in our study exhibited such decline. Some dropped out to find work; others joined gangs.

The good news: a quarter of the students sustained high academic performance over the five years of the study, and another 11 percent showed significant improvement. While they experienced the same initial shock of migration, they tended to be enrolled in supportive schools, to have caring teachers, and to develop informal mentorships with coaches, counselors or ministers. In addition, other researchers, like Philip Kasinitz, John H. Mollenkopf, Mary C. Waters and Jennifer Holdaway, have found that the second generation — American-born kids of immigrant parents — assimilate, and even excel, to a greater extent than the “1.5 generation” (children who immigrate in or before their early teens).

Whatever motivated the Tsarnaev brothers surely is not the fault of the schools and may never be known. Among some of the distinctive features of their case are family estrangement, multiple relocations across countries and, possibly, religious radicalization.

But the broad lesson — assimilating immigrant students into the fabric of society through academic, psychological and other supports — should inform educators and policy makers in the decades ahead, when immigrants and their children will account for most of the nation’s population growth. One successful model is the Internationals Network for Public Schools, where educators focus on students’ distinct needs and develop authentic connections with their families.

Taking in what Emma Lazarus called the “wretched refuse,” including asylum seekers like the Tsarnaev brothers, without providing a scaffold of support undermines the promise of America.