Class-Size Caps, Sorting, and the Regression-Discontinuity Design
研究学校对班级规模的选择和家庭对学校的选择如何影响基于断点回归的班级规模效应估计，发现学校在班级规模上限处调整价格或招生以避免增加班级，导致断点回归假设失效。
This paper examines how schools' choices of class size and households' choices of schools affect regression-discontinuity-based estimates of the effect of class size on student outcomes. We build a model in which schools are subject to a class-size cap and an integer constraint on the number of classrooms, and higher-income households sort into higher-quality schools. The key prediction, borne out in data from Chile's liberalized education market, is that schools at the class-size cap adjust prices (or enrollments) to avoid adding an additional classroom, which generates discontinuities in the relationship between enrollment and household characteristics, violating the assumptions underlying regression-discontinuity research designs.