According to a recent study published by the National Center for Education Statistics (NCES), public school students are outperforming their private school counterparts in fourth grade mathematics and have equaled “private school students in fourth grade reading and eighth grade math.” However, as Shanea Watkins, Policy Analyst in Empirical Studies in the Center for Data Analysis at The Heritage Foundation, explains, these results require greater scrutiny. Some commentators that reference the NCES report believe the study points to a causal relationship—that attending a public school will cause higher academic achievement in math. However, the study focuses on data provided by...