Lerner Center for Public Health Promotion and Population Health
Population Health Research Brief Series
More Girls in the Classroom Improves Adolescent Mental Health
Monica Deza and Maria Zhu
December 2025
Abstract
Adolescent mental health has long been an important public health concern, with recent data showing that 29% of high school students reported poor mental health and 20% seriously considered suicide in the past year. What role does the school environment play in shaping adolescent mental health?
This brief examines how the mix of boys and girls in a classroom affects student mental health and wellbeing. The authors find that classrooms with more girls have better mental health outcomes for both boys and girls. Boys in classes with more female peers are 10% less likely to experience clinical depression and feel more connected to school. Boys benefit through stronger friendships, while girls benefit through better grades and improved self-image.
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