LOS ANGELES -- Researchers have some new advice for high school students who want better grades: Become friends with academically oriented classmates.Researchers surveyed all members of the junior class at Maine-Endwell High School in Endwell, N.Y., and asked students to rate each of their classmates as either a "best friend," a "friend," an "acquaintance" or someone they didn't know. They got responses from 92 percent of students and used them to reconstruct the students' social networks.The research team also obtained the grade point averages for all 158 students in January 2011 and January 2012. For the analysis, those GPAs were converted into class rankings. Then they compared the rankings of each student to those of their best friends, friends and acquaintances.Sure enough, the researchers found a linear relationship between a student's grades and the academic environment of their social network. If a student's class ranking at the start of the study was higher than usual for her social network, it tended to fall over the course of the year.The most significant influence appeared to be the grades of those labeled as "friends." To explain this, the researchers hypothesized that the grades of "best friends" made little difference in the equation because they were probably very similar to start with. But the gaps between students and their "friends" were bigger, so there was more opportunity for influence.