Program evaluations that measure the effects of online charter schools on student achievement will be biased if they fail to account for unobserved differences between online students and students in the comparison group. There are theoretical and empirical reasons to believe that students who enroll in online schools disproportionately face challenges that are not accounted for in administrative data. This paper investigates some of the negative factors that motivate parents to enroll in online schools. We combine data from an online charter school survey—that asked why parents decided to enroll in online schooling—with three years of achievement and demographic data. We find that students whose parents indicated they selected online schools for negative reasons made statistically significantly lower ELA gains, even after controlling for prior achievement, race, gender, free lunch status, and special education status. We conclude that other observational analyses of online charter schools, such as CREDO (2015), will be biased and unreliable if they fail to properly control for reasons students select those schools
