Yes, Students Getting Shut Out of Courses is a Big Deal for Student Success

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We instinctively recognize that students being unable to enroll in the classes they want or need is a problem. In fact, it’s often cited by students as one of their biggest frustrations.

One reason oversubscribed courses have long been seen as a problem is our intuitive sense that they prevent students from enrolling in the classes they need to graduate on time. Traditionally, however, research  suggested that this wasn’t the case, that being shut out of courses had little to no measurable impact on time to graduation.

But more recent and innovative research has challenged that assumption, shedding light on the significant ways course shutouts can affect student success.

These effects include increasing the likelihood that a student will stop out or transfer to another institution, decreasing the likelihood that they will ever take that course, or any course in that discipline, reducing women’s participation in STEM fields, and even affecting post-graduation earnings. These are serious consequences with meaningful implications for both students and institutions.

In this first of a two-part series, I’ll explore the research on how being shut out of courses affects student success. In the next post, I’ll look at how online learning might help mitigate the effects of oversubscribed courses.

Innovative research and broader questions

A recent paper by economists at Purdue and Brigham Young brought fresh attention to this issue. It builds on several years of research by the co-authors and complements an earlier body of work by economists analyzing data from Foothill-De Anza Community College in California.

One of the most interesting aspects of both research efforts is their use of innovative research designs. Measuring the impact of not getting into a course is inherently tricky, how do you assess the effect of an opportunity that was never available? Simply comparing the outcomes of students who were waitlisted or denied access to a course isn't reliable. Registration priority is often based on factors like class standing or accumulated credits, so comparing shut-out students with those who got in is rarely a like-for-like analysis. And while randomized controlled trials, the gold standard for many researchers, could address some of these issues, they raise serious ethical concerns in this context.

Both sets of studies tackle these challenges in different but equally creative ways. Their methods are complex, and I’ve done my best to summarize them here. For those interested in the details, I encourage you to read the original research.

The earlier research , conducted by Silvia Robles and colleagues, used course registration data from Foothill-De Anza collected between 2002 and 2010. They supplemented this with data from the National Student Clearinghouse to assess the impact of being unable to enroll in a waitlisted course. By analyzing course waitlist logs, they compared students who ultimately got off the waitlist to those who didn’t.

The more recent research by Mumford et al. draws on a unique situation at Purdue University. In 2018, due to an unusually large incoming class, Purdue implemented a batch assignment algorithm to manage course registration for first-year students. The algorithm used students’ ranked course preferences, course availability, and schedule constraints to randomly assign course schedules. As a result, access to oversubscribed courses was distributed more evenly, and whether or not a student was shut out of a course became essentially random.

To take advantage of this setup, the researchers ran 1,000 simulations of the algorithm to estimate the probability of course shutouts. This allowed them to ensure that whether a student was shut out of a course was uncorrelated with individual characteristics like race or accumulated credits, in other words, effectively random. While not a perfect randomized controlled trial, the result was a sample that came remarkably close: a randomly distributed group of students, some of whom were shut out of a desired course for reasons unrelated to their background or academic standing.

Analyzing 15,112 course-level observations for 8,566 students in Fall 2018, they found that 49% of students were assigned their preferred schedule, while 51% were shut out of at least one of their top six requested courses.

So what did the two sets of researchers find?

The impact of shutouts?

Looking at community college students, Robles found that even though being shut out of a course did not impact students speed to graduation, it did affect course taking behavior and, ultimately, retention. Not being able to enroll in a class not only reduced course-taking behavior but, more significantly, increased the likelihood of stopping out during the affected semester by 25%.

Among students who did not request an oversubscribed course, nearly 10% took zero courses during the term, effectively stopping out. In comparison, 13% of students who were shut out of a course did the same, representing a 25% increase in the stop-out rate.

Over time, Robles also found that students who were shut out of courses were more likely to transfer to other institutions than those who were not.

But this tended to vary sharply by race and ethnicity.

Similarly, Mumford et al., in their study at Purdue University, found that being shut out of a course had a significant impact on students’ course-taking behavior.

Being shut out of a course did not affect the overall four-year graduation rate. However, it did result in students completing fewer credits that semester and reduced the likelihood of majoring in a STEM field. While none of these effects are good in themselves, the results become more striking when broken down by gender.

To summarize the impacts of course shutouts across both bodies of work.

The usual caveat lector

Of course, there are some limitations to this research.

Single-institution studies: Both studies rely on data from a single institution. While the fact that these institutions are quite different—a large research university (Purdue) and a community college (Foothill-De Anza), helps mitigate this limitation, it still raises questions about generalizability.

Sample representativeness: The Purdue study by Mumford et al. focuses on first-term enrollments of freshman students, while the community college study includes only full-time students. Broader samples might yield different results. Expanding this research to include other institutions and a wider range of student types would provide a more comprehensive picture.

Self-reported earnings data: The earnings data used in the Mumford study were self-reported, which may not be fully representative. It’s also reasonable to assume that this data could be biased upward, potentially underestimating the true impact of being shut out of a course.

Why this matters

As both sets of researchers point out, oversubscribed courses are often a symptom of budget constraints at colleges and universities. Even in the absence of such constraints, community college courses are frequently oversubscribed. As Robles study notes , 49% of all course sections had at least one student on the waitlist, including 68% of STEM courses, 60% of social science courses, and 50% of arts and humanities courses. As we enter a period of serious budget cuts, we’re likely to see even more students unable to enroll in the courses they need or want.

Even if oversubscribed courses don’t directly impact four-year graduation rates, the broader effects on students and, by extension, institutions, are significant, especially when we examine differential impacts by gender and ethnicity.

Being shut out of courses increases the likelihood of students dropping out or transferring. This slows their progress toward a credential and contributes to the growing population of “Some College, No Credential” students, individuals burdened with debt but lacking the earning power of a degree. For institutions, especially in an era of demographic decline, losing students to attrition or transfer means lost revenue and missed opportunities for retention.

At the same time, institutions face mounting pressure from state governments, federal agencies, and the public to demonstrate accountability. Any factor that meaningfully impacts student outcomes deserves serious attention. And as states push institutions to steer students toward certain fields, like healthcare and STEM, course shutouts that deter students from those majors can undermine institutional goals and planning.

But for me, the most important takeaway from this research is the value of taking a wide-angle view when measuring impact. Rather than fixating on a single outcome, such as on-time graduation, both research teams show how being shut out of a course can make the student journey more difficult and less rewarding. If we’re serious about improving student success, we have to examine the full experience, not just the finish line.

In my next post on this topic, I’ll explore how colleges and universities are using online learning to help meet course demand and ease the effects of oversubscription.

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