Unequal educational outcomes for children with similar early childhood vocabulary but different socio-economic circumstances

Background In a purely meritocratic society, educational outcomes would reflect ability and only ability. Vocabulary size is a common measure of cognitive ability that predicts educational outcomes but is confounded with socioeconomic circumstances (SEC). Methods In preregistered analyses of the nationally representative UK Millennium Cohort Study data (N = 15,576), we used a series of multiple linear and logistic regression analyses to investigate the predictive value of age-5 vocabulary for age-16 educational outcomes and assess whether socioeconomic circumstance moderated this relation. Results We show that age-5 vocabulary strongly predicted age-16 educational attainment, even after adjusting for both SEC and caregiver vocabulary (OR = 1.62, 95% CIs = [1.52; 1.72]; β = .22, 95% CIs = [0.19; 0.24]). SEC also predicts educational attainment (OR = 2.05, 95% CIs = [1.92; 2.19]), and modifies the association between vocabulary and educational attainment, whereby a larger vocabulary was most advantageous for those in middle SEC groups (interaction term OR = 1.09 [1.03; 1.15]). Conclusions Early child vocabulary is a strong predictor of children's educational outcomes – even when controlling for proxy measures of the home environment and genetics. Nonetheless, children who enter school with strong vocabulary skills but disadvantaged socioeconomic circumstances still have only about a 50/50 chance of gaining gateway qualifications at age 16.