Good grades? It's all in who you know: Having friends who attend the same school is key, study shows

It turns out that the missing ingredient could be the friends a child keeps, specifically their in-school friends, the ones who sweat the same tests and homework and complain about the same teachers, rather than those they may make outside of school.

UCLA professor of psychiatry and senior study author Andrew J. Fuligni and first author Melissa R. Witkow, a former graduate student of Fuligni's, report in the online edition of the Journal of Research on Adolescence that adolescents with more in-school friends than out-of-school friends had higher grade-point averages and -- complementing this finding -- that those with higher GPAs had more in-school friends.

The authors found that these associations were similar for boys and girls and cut across all ethnic groups.

Drawing from three Los Angeles-area high schools, the researchers recruited 629 12th-grade students, split almost evenly by sex, with an average age of 18; no single ethnic group predominated. The students filled out a questionnaire, then kept a diary in which they logged such activities as time spent studying, time spent with in-school or out-of-school friends, and other activities.

Roughly speaking, the more in-school friends a child had, the higher the GPA.

"We found that within an adolescent's friendship group, those with a higher proportion of friends who attended the same school received higher grades," said Witkow, now an assistant professor of psychology at Willamette University. "This is partially because in-school friends are more likely to be achievement-oriented and share and support school-related activities, including studying, because they are all in the same environment."

This is not to dismiss or put a negative spin on a child's friends from outside school, Witkow said. "These friendships are still important in terms of fulfilling adolescents' social needs, and they are not necessarily always detrimental to achievement. For instance, friendships that form in academic settings outside of school, such as at an enrichment class, may very well promote achievement."

The next step, the authors say, is further research to better understand how out-of-school friendships are formed and how they are different from in-school friendships. The authors hope to expand their studies to draw upon younger ages and earlier grades.

Still, the findings from this work suggest that, on average, in-school friendships help support achievement because of the ways in which they engage adolescents in the school experience, Witkow said. The bottom line? Know who your child's friends are.

Funding for the research was provided by the Russell Sage Foundation. The authors report no conflict of interest.