A new Harvard study shows that immigrant boys and girls fare very differently in the outside world.

When it comes to schooling, the Herrera boys are no match for the Herrera girls. Last week, four years after she arrived from Honduras, Martha, 20, graduated from Fairfax High School in Los Angeles. She managed decent grades while working 36 hours a week at a Kentucky Fried Chicken. Her sister, Marlin, 22, attends a local community college and will soon be a certified nurse assistant. The brothers are a different story. Oscar, 17, was expelled two years ago from Fairfax for carrying a knife and later dropped out of a different school. The youngest, Jonathan, 15, is now in a juvenile boot camp after running into trouble with the law. "The boys get sidetracked more," says the kids' mother, Suyapa Landaverde. "The girls are more confident."

This is no aberration. Immigrant girls consistently outperform boys, according to the preliminary findings of a just-completed, five-year study of immigrant children—the largest of its kind, including Latino, Chinese and Haitian kids—by Marcelo and Carola Suarez-Orozco of the Harvard Graduate School of Education. Though that trend holds for U.S.-born kids as well, the reasons for the discrepancy among immigrants are different. The study found that immigrant girls are more adept at straddling cultures than boys. "The girls are able to retain some of the protective features of [their native] culture" because they're kept closer to the hearth, says Marcelo Suarez-Orozco, "while they maximize their acquisition of skills in the new culture" by helping their parents navigate it.

Consider the kids' experiences in school. The study found that boys face more peer pressure to adopt American youth culture—the dress, the slang, the disdain for education. They're disciplined more often and, as a result, develop more adversarial relationships with teachers—and the wider society. They may also face more debilitating prejudices. One teacher interviewed for the study said that the "cultural awareness training" she received as part of her continuing education included depictions of Latino boys as "aggressive" and "really macho" and of the girls as "pure sweetness."

Gender shapes immigrant kids' experiences outside school as well. Often hailing from traditional cultures, the girls face greater domestic obligations. They also frequently act as "cultural ambassadors," translating for parents and mediating between them and the outside world, says Carola Suarez-Orozco. An unintended consequence: "The girls get foisted into a responsible role more than the boys do." Take Christina Im, 18, a junior at Fairfax who arrived from South Korea four years ago. She ranks ninth in a class of 400 students and still finds time to fix dinner for the family and work on Saturdays at her mother's clothing shop. Her brother? "He plays computer games," says Im.

The Harvard study bears a cautionary note: If large numbers of immigrant boys continue to be alienated academically—and to be clear, plenty perform phenomenally—they risk sinking irretrievably into an economic underclass. Oscar Herrera, Martha's dropout brother, may be realizing that. "I'm thinking of returning to school," he recently told his mother. He ought to look to his sisters for guidance.