A UCLA study done on 629 high school seniors, in 3 different Los Angeles High Schools, suggests that having friends is super important for good grades. The more friends you have in-school versus out of school the better the GPA. The study asserts this true regardless of ethnicity or gender.
"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."
Don't worry, the researchers don't want you to chuck your kids out-of-school friends just yet. But, you might want to keep a good eye on them just the same.