The Girl Next Door: The Effect of Opposite Gender Friends on High School Achievement
研究发现，学生异性朋友比例越高，高中GPA越低。该效应在16岁以上学生中涉及所有科目，在更年轻学生中仅影响数学和科学成绩，可能通过课堂注意力和课外恋爱关系发挥作用。
This paper finds that a student's share of opposite gender school friends negatively affects high school GPA. It uses the gender composition of schoolmates in an individual's neighborhood as an instrument for the gender composition of an individual's self-reported friendship network. The effect occurs across all subjects for students older than 16, but only in mathematics and science for younger students. Additional results indicate effects may operate inside the classroom through difficulties getting along with the teacher and paying attention, and outside the classroom through romantic relationships.