The Development of Inequality During Primary Education: Investigating the Genetic and Environmental Sources Underlying Learning Differences

Are differences in educational performance between pupils at the start of schooling – and their underlying genetic and environmental sources – reproduced, accumulated, or compensated over the primary school career? I investigate this using reading and mathematics test scores of ~5,500 same-sex and opposite-sex twin pairs, identified in the Netherlands Cohort Study on Education (Grades 1-5). Biometric latent growth models show, first, that most of the achievement gap is already present at the start of education and related to genetic variance. Second, this initial achievement gap is somewhat compensated over time. It varies by domain whether this leveling is related to decreasing genetic or environmental differences. For reading, genetic differences decrease, whereas environmental differences are reproduced. For mathematics, the opposite is true: environmental differences decrease, and genetic differences are reproduced. Third, new performance differences, unrelated to the initial gap, are emerging over time, mostly related to genetic differences. These new gaps outweigh the leveling of the initial gap, resulting in an increase in the total achievement gap during primary education.