At many colleges in the United States, incoming students are required to take placement tests in basic skills such as math and reading. Those who score below a cut-off are required to take remedial coursework. Is there solid evidence about the effectiveness of remedial math courses? I'm particularly interested in community colleges.
The only empirical study I was able to turn up was Calcagno 2008. The method they used was to examine data from Florida community colleges to look for evidence of a discontinuity in average educational outcomes as a function of placement test scores, at the cut-off. The reasoning is that a student who scores at the cut-off score $x$ has almost the same math skills as one who scores $x-1$ and is forced into remediation, but would have a worse educational outcome because of not getting remediation. The result seems to be that math students who get remediation don't do better in later math coursework, and aren't more successful in college.
The subject seems to be controversial, however. Are there other studies that do support remediation?
At the community college where I teach, it wouldn't be surprising to me if remediation was uncorrelated with later success, simply because our curriculum has so much review built into it. For example, a student who starts at a low math level and gradually climbs up through our sequence will probably be led over and over again through reviews of the same topics, such as the properties of the reals or how to solve multiple equations in multiple unknowns.
Calcagno and Long, "The Impact of Postsecondary Remediation Using a Regression Discontinuity Approach: Addressing Endogenous Sorting and Noncompliance," National Center for Postsecondary Education, 2008, http://ies.ed.gov/director/conferences/08ies_conference/pdf/calcagno_long.pdf