How Extending Time in Developmental Math Impacts Student Persistence and Success: Evidence from a Regression Discontinuity in Community Colleges

Improving the outcomes of students in developmental or remedial math remains a puzzle in higher education. Nationally, about 60 percent of community college students take remedial courseswork, most likely because they are deemed academically under-prepared for college level courses (Bailey, Jeong, & Cho, 2010). Of these students, only about 40 percent persist and complete the gatekeeper college-level math courses typically required to earn postsecondary credentials. The lower a student’s initial level of math remediation, the less likely that student will earn desired credentials or transfer to a four-year institution (Bahr, 2012; Fong, Melguizo, & Prather, 2015). While some of these outcomes can be explained by students’ academic preparation, they also may be related to the amount of time students spend in remediation (Edgecombe, 2011), to the additional costs of taking remedial courses (Melguizo, Hagedorn, & Cypers, 2008), or to the quality of instruction in these courses (Grubb, 1999). The puzzle is that the very intervention that is aimed at preparing students to be successful in gatekeeper college-level courses may at the same time be an obstacle and deterrent to their persistence in college.

Concerns with low persistence and completion rates have motivated proponents of reform to reconsider the delivery of developmental math (Burdman, 2012; Rutschow & Schneider, 2011). Moving away from the traditional sequence of multiple semester-long courses taught in lecture-based formats, practitioners and policy-makers have explored alternative models of delivery that accelerate student progress, contextualize curriculum and instruction, or provide additional supports to students in developmental courses (Rutschow & Schneider, 2011). But in an examination of math course offerings in a set of urban community colleges in California, Kosiewicz, Ngo, and Fong (2016) found that a far more prevalent model of delivery was to extend time in remediation, essentially slowing down the delivery of math content. Specifically, some of the colleges implemented placement policies that assigned students to either extended two-semester¹ or traditional one-semester elementary algebra courses that serve as prerequisites for college-level math. Both types of courses start with roughly the same content from day one, but the extended algebra courses move at a slower pace and force students to make two enrollment decisions: one to enroll in the first half of the course and another to enroll in the second.

Lengthening the amount of time in math in this way is thought to be an intervention that improves academic achievement. The underlying logic is that lower-skilled students may need more time and instruction to master necessary algebraic concepts (Aronson, Zimmerman, & Carlos, 1999). However, while there is some evidence that increasing the amount of instructional time in algebra benefits middle and high school students (Cortes, Goodman, & Nomi, 2015; Taylor, 2014), it is unclear whether this practice is beneficial to community college students, for whom the additional costs in terms of time and money may outweigh the benefits of remediation. Does extending time in algebra by a semester help community college students persist and succeed in developmental math and college?

We investigate this research question using administrative data from four large urban community colleges in California. The nature of math course placement policies within these colleges provides the opportunity to use a regression discontinuity (RD) design to estimate the impact of assigning students to extended math courses relative to single-semester courses on student achievement outcomes. While other researchers have used RD designs in the setting of developmental math to identify the effects of placement in remediation, they have predominantly examined placement into disparate math courses (e.g., the effects of placement in elementary versus intermediate algebra on student outcomes). Thus it is difficult to disentangle whether differences in outcomes are attributable to differences in time spent in remediation or to the academic preparation within remedial courses. This study is unique because we are able to focus on the effects of requiring students to spend additional time in math remediation. Students around the placement cutoffs are considered statistically identical, but one group must take two semesters of algebra instead...