The more male classmates, the worse: How male peers harm academic performance of a student.

This paper examines the influence of male peer proportion on a student's academic performance. The sex ratio at 10–14 was 117.16 in 2011, and it has increased to 119.1 in 2019. The sex ratio imbalance at 10–14 tends to expand. This paper uses China Education Panel Survey (CEPS) 2013–14 and 2014–15. Considering the selection bias, this paper restricts the sample to schools that satisfy randomly-assignment conditions. The results highlight that students with a high proportion of male classmates have a lower performance in Mathematics and English but not Chinese. To explain these effects, this paper uses three channels to interpret: (1) cognitive ability, (2) learning effort, and (3) the quality of the classroom environment. It provides implications for policymakers and school administrators to take precautions in advance. [ABSTRACT FROM AUTHOR]