One goal of a 1965 U.S. immigration law, which also abolished severe restrictions against immigration from regions such as Asia, was to give preference to professionals with specialized skills. Partly as a result, a little more than half of Chinese immigrants to the United States have a college degree or higher, versus less than 10 percent of adults in China in recent years, Ms. Lee said. They have tended to prioritize that their children earn straight As; attend a good college; and become a doctor, lawyer, scientist or engineer, the authors wrote. They have also shared information about things like SAT tutors and A.P. courses with their less educated Asian-American peers.

Another factor is the so-called model minority stereotype — that Asians as a group are supposed to be smart, successful and hard-working. This image masks high poverty and dropout rates among some Asian ethnic groups, yet as with all stereotypes, it can lead people to act in biased ways. Teachers tend to give Asian-American students higher grades and funnel them into advanced programs, the researchers found. Often, lower-performing students have risen to meet these expectations of them, an effect social scientists refer to as stereotype promise.

For Asian-American boys, these influences change in adolescence, Ms. Hsin found, a time when children become more aware of their gender identity and are more influenced by peers. They also have to fight a pernicious perception that they are not masculine enough.

“The model minority myth frames Asian boys as being kind of nerdy, caring too much about doing well, so that may cause them to become less academically attached,” Ms. Hsin said. “It’s not as stigmatizing for Asian girls because if you’re good at school and you really care, that kind of plays along with what you should be doing as a girl anyway.”

The new study offers a clue about how much school environments affect boys’ academic achievement. Ms. Hsin found that the gender gap for Asian-Americans in high school was smaller in schools that were less sports-focused, and where boys did better over all.

Other studies have also pinpointed the importance of the school and social environments, especially for boys.

One working paper found that the best-performing students had a combination of behaviors typically considered male and female. It used nationally representative survey data about gender norms for about 12,000 high school students, linked with their high school transcripts. The most traditionally feminine girls and the most masculine boys had the lowest grades.