Spending more time at school benefits the best-performing pupils disproportionately, according to a new study.
The researchers used data from the Early Childhood Longitudinal Study – Kindergarten Cohort (ECLS-K). This included more than 20,000 children who entered 1,000 kindergarten (Year 1) programmes in schools across the US in 1998. Children were given maths and reading tests in the autumn and spring. Because there was essentially random variation in when these tests were delivered, there were variations in the amount of teaching time between the two tests. The researchers used this to analyse the progress made, but also the difference in progress among the different percentiles within the class.
They found that, on average, reading scores increase by 1.6 test score standard deviations (SD) during a standard 250 day school year. However, readers in the bottom 10% increased by only 0.9 test score SD, while those in the top 10% increased by 2.1 test score SD. A similar result was found for mathematics. The authors suggest that policy makers, practitioners, and analysts must consider the average and distributional impacts of educational inputs and interventions.
Source: What Differences a Day Can Make: Quantile Regression Estimates of the Distribution of Daily Learning Gains (2015), Institute for the Study of Labor (IZA).