Association for Public Policy Analysis & Management

Human capital theory has little to say about whether maturity and family background are complements or substitutes. This question is crucial in the context of public policies that reduce or increase the maturity of school children. In order to estimate the impact of maturity on student achievement, we exploit the fact that in 2009, the state of North Carolina shifted the date by which students could enter public school from October 16 to August 31. The result of this 45-day shift was that children born between September 1 and October 16 were effectively "redshirted" and forced to delay entry into school by one year. North Carolina joined more than a dozen states in recent years by shifting school entry dates earlier in the year, ostensibly to reduce the strain on state budgets in the post-Great Recession era by temporarily reducing average daily attendance.

We estimate the impact of North Carolina’s reform on academic achievement by race/ethnicity using difference-in-differences and instrumental variables approaches that contrast pre- and post-reform cohorts. Using administrative records for students in the Wake County Public School System (WCPSS; the state's largest district) and their results on the state’s End-of-Grade summative math and reading tests, we find that, on average, students born between Sep. 1 and Oct. 16 gained 0.52 years of age at test and their test scores improved by 0.17 standard deviations (SD). The policy shift reduced the achievement gap by 20% between non-minority and minority students. The larger impact of the shift on minority students relative to non-minority students was due to a greater average gain in age (0.58 vs 0.46 years, respectively) and a larger average impact on test scores per year of age at test (0.42 SD vs 0.23 SD, respectively) The evidence suggests the greater per-unit impact for minority students is not explained by lower average income among minorities, as the average impact is greater in schools with fewer students receiving free or reduced-price lunch. We conclude that, among WCPSS students directly affected by North Carolina’s reform, greater maturity at the start of school helps minorities more and therefore contributes to narrowing the achievement gaps relative to non-minority students.

Our results suggest that the reduction in achievement gaps between White and minority students is in part the result of minority students gaining more maturity—prior to the reform they were less likely to "redshirt" than White students. More importantly, the gain in test scores per unit of maturity gained for minority students is roughly double the gain for White students, supporting the idea that maturity is a substitute for more affluent family background. Additionally, the evidence suggests that the greater per-unit impact for minority students is not simply due to a lower average income among minorities, as the impact of maturity is greater in higher-income schools. Our findings will also include relative-age impacts on behavioral, civic, and additional academic outcomes for cohorts subsequent to the state's policy shift.