Rapid emergence of a maths gender gap in first grade

Preventing gender disparities in mathematics is a worldwide preoccupation^1,2. In infancy and early childhood, boys and girls exhibit similar core knowledge of number and space^3-8. Gender disparities in maths are, therefore, thought to primarily reflect an internalization of the sociocultural stereotype that 'girls are bad at maths'. However, where, when and how widely this stereotype becomes entrenched remains uncertain. Here, we report the results of a 4-year longitudinal assessment of language and mathematical performance of all French first and second graders (2,653,082 children). Boys and girls exhibited very similar maths scores upon school entry, but a gender gap in favour of boys became highly significant after 4 months of schooling and reached an effect size of about 0.20 after 1 year. These findings were repeated each year and varied only slightly across family, class or school type and socio-economic level. Although schooling correlated with age, exploiting the near-orthogonal variations indicated that the gender gap increased with schooling rather than with age. These findings point to the first year of school as the time and place where a maths gender gap emerges in favour of boys, thus helping focus the search for solutions and interventions.