Whether a family attends religious services has as much of an impact on a teen's grade point average as whether the student's parents earned a college degree, a University of Iowa study indicates.

Researchers found that on average, students whose parents received a four-year college degree average a GPA .12 higher than those whose parents only completed a high school education. Students who attend religious services weekly average a GPA .144 higher than those who never attend services, said Jennifer Glanville, a sociologist in the UI College of Liberal Arts and Sciences who led the study.

Other studies have noted a link between religious service attendance and positive educational outcomes, but this is one of the first to look at why.

The study confirmed four reasons church-going teens tend to have more success in school: they have regular contact with adults from various generations who serve as role models; their parents are more likely to communicate with their friends' parents; they develop friendships with peers who have similar norms and values; and they're more likely to participate in extracurricular activities.

Together, these factors account for about half of the predicted effect of religious attendance on educational outcome, controlling for other important factors like socioeconomic status and family structure, Glanville said.

"There are two directions you can go with this research," she said. "Some might say this suggests that parents should have their kids attend places of worship. Or, if we use it to help explain why religious participation has a positive effect on academics, parents who aren't interested in attending church can consider how to structure their kids' time to allow access to the same beneficial social networks and opportunities religious institutions provide."

Glanville and colleagues David Sikkink and Edwin Hernandez of the University of Notre Dame analyzed data from the National Longitudinal Study of Adolescent Health, a nationally representative sample of 7th- through 12th-graders that began in 1994. Students from 132 schools in 80 communities participated.

Overall, teens that attended services regularly demonstrated more positive educational outcomes in three areas: they had higher GPAs, a lower dropout rate, and greater school attachment (defined as the degree to which students feel like a part of the school and feel happy to be a part of it). Religious-service attendance had the same effect across all major denominations, the study showed.

"For typical teens in the study, the probability of dropping out of high school for those who attend religious services and youth activities at least once a week is .05," Glanville said. "For teens who never attend services, the probability is .084, over 60 percent greater."

Researchers found that religious involvement can impact the kind of friends students make, which in turn influences academics. Teens were asked to name their five best male and female friends; the researchers evaluated the qualities of friends within their network. Kids who attended church were more likely to have friends with higher GPAs who skipped school less often, Glanville said.

"We know roughly half of American teens regularly participate in some kind of religious organization," Glanville said. "So it's important to understand what aspects of religious involvement can benefit adolescents in order to enhance their school success during a difficult but critical period of development."

The study, published in the winter 2008 issue of The Sociological Quarterly, also looked at whether the teens said religion was important to them.

"Surprisingly, the importance of religion to teens had very little impact on their educational outcomes," Glanville said. "That suggests that the act of attending church -- the structure and the social aspects associated with it -- could be more important to educational outcomes than the actual religion."