Fuzzy regression-discontinuity evaluations of college remediation often find negative and null estimates of local average treatments effects (LATEs), but with substantial heterogeneity. We find that a remedial quantitative skills course at Wellesley College has a modestly positive LATE on participation in mathematically intensive fields of study—including the sciences, mathematics, and economics courses. Yet, LATEs are a weighted average of average causal effects (at the passing cutoff) in two principal strata: students who voluntarily comply with remediation, and those who are coerced to comply after scoring below the cutoff on an optional retest. In the retest sample, we show that average causal effects are close to zero among (1) coerced compliers, and (2) never-takers. By implication, there are even larger effects among a smaller group of voluntary compliers at the cutoff. The results help interpret the mixed findings in the literature, in which compliance varies widely, and demonstrate methods for assessing external validity in fuzzy-discontinuity designs.

In fall 2014, Wellesley College began mandating pass/fail grading for courses taken by first-year, first-semester students, although instructors continued to record letter grades. We identify the causal effect of the policy on course choice and performance, using a regression-discontinuity-in-time design. Students shifted to lower-grading science, technology, engineering, and mathematics (STEM) courses in the first semester, but did not increase their engagement with STEM in later semesters. Letter grades of first-semester students declined by 0.13 grade points, or 23 percent of a standard deviation. We evaluate causal channels of the grade effect—including sorting into lower-grading STEM courses and declining instructional quality—and conclude that the effect is consistent with declining student effort.