Boys at risk of academic decline? Evidence from a longitudinal study

Using a unique longitudinal dataset tracking 116,026 students from Grade 1 to Grade 10, we examine the emergence, evolution, and drivers of gender gaps in academic achievement. We document large and widening female advantages: in English, the gap grows from 0.2 to 0.65 standard deviations (SD), and in math, from 0.1 to 0.4 SD. These patterns are consistent across cohorts, grades, and performance quartiles, and remain robust to the inclusion of classroom fixed effects. Adjusting for family background and teacher characteristics further enlarges the estimated gaps, particularly in higher grades. Importantly, the gaps persist even among opposite gender siblings raised in the same household. Leveraging the random assignment of students to classrooms, we assess the causal effects of teacher gender and peer composition, but find these factors account for little of the observed gaps. In contrast, controlling for prior achievement-a proxy for baseline ability and unobserved individual heterogeneity-substantially attenuates the gaps. To further probe individual-level variation, we analyze traits such as diligence, hard work, and attentiveness among opposite-gender sibling pairs. We find that sisters consistently outperform their brothers on these dimensions, with disparities widening as students progress through grades. Taken together, our findings suggest that individual traits may play a central role in driving the widening gender gap over time.