- Michael Gilraine
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This paper identifies the achievement impact of installing air filters in classrooms for the first time. To do so, I leverage a unique setting arising from the largest gas leak in United States history, whereby the offending gas company installed air filters in every classroom, office and common area for all schools within five miles of the leak (but not beyond). This variation allows me to compare student achievement in schools receiving air filters relative to those that did not using a spatial regression discontinuity design. I find substantial improvements in student achievement: air filter exposure led to a 0.20 standard deviation increase in mathematics and English scores, with test score improvements persisting into the following year. Air testing conducted inside schools during the leak (but before air filters were installed) showed no presence of natural gas pollutants, implying that the effectiveness of air filters came from removing common air pollutants and so these results should extend to other settings. The results indicate that air filter installation is a highly cost-effective policy to raise student achievement and, given that underprivileged students attend schools in highly polluted areas, one that can reduce the pervasive test score gaps that plague public education.
While school choice may enhance competition, incentives for public schools to raise productivity may be muted if public education is viewed as imperfectly substitutable with alternatives. This paper estimates the aggregate effect of charter school expansion on education quality while accounting for the horizontal differentiation of charter school programs. To do so, we combine student-level administrative data with novel information about the educational programs of charter schools that opened in North Carolina following the removal of the statewide cap in 2011. The dataset contains students' standardized test scores as well as geocoded residential addresses, which allow us to compare the test score changes of students who lived near the new charters prior to the policy change with those for students who lived farther away. We apply this research design to estimate separate treatment effects for exposure to charter schools that are and are not differentiated horizontally from public school instruction. The results indicate learning gains for treated students that are driven entirely by non-horizontally differentiated charter schools: we find that non-horizontally differentiated charter school expansion causes a 0.05 SD increase in math scores. These learning gains are driven by public schools responding to increased competition.