Impact of Class Size on Learning Outcomes?

Someone posted that question on the Professional and Organizational Development (POD) listserv this morning. I thought you might like to know how I responded:

There is no general relationship between class size and learning outcomes. (Think of a self-help book that sells millions of copies, or a PBS program on the civil war, if you'd like an analogy. It's possible for people to learn relatively sophisticated lessons even when "class sizes" are enormous. And the learning outcomes of presentation, whether delivered by book, video or by uninterrupted lecturing, aren't affected much by class size).

The research only gets interesting when you begin by specifying some teaching/learning activity and then asking about

1. the impact of class size on its feasibility, and
2. the outcome when that pedagogy is in successful use.

I call these three elements of resource/technology (class size), teaching/learning activity, and outcomes a "triad." The resource or technology offers choices. The activity is what people actually did with the choices. And the outcomes result from those activities. (That simple grammar suggests some powerful questions for the scholarship of teaching and learning in any course or set of courses.)

Some important teaching/learning activities do far better in small classes, and some learning outcomes are much easier to achieve with those activities. (e.g., seminar style discussion; activities that require personal coaching by an expert) But the threshold (the class size where the pedagogy breaks down) varies: I used to work at Evergreen where seminars of 20 students worked pretty well. But a master class in violin would certainly work much better with a 1:1 ratio than with 20:1.

Of course, if you summarize studies of class size that include all sorts of pedagogies and all sorts of outcomes, some of which involve lots of interaction, you'll find a small relationship between class size and outcomes. Which is what Pascarella and Terenzini report in their synthesis of research on learning, How College Affects Students.

Your question is an example of a larger class of questions about the relationships of inputs or technologies to learning outcomes (e.g., how does the size of the library affect learning outcomes? distance learning v. campus classrooms? highly paid profs v. low paid profs?) The role of resources in learning, even a scarce resource such as the attention a professor might pay to a student, is to create possibilities for action.

The power comes from the teaching/learning activities - what faculty and students actually do in those classes. That's why you'll see relatively significant findings on studies of learning where the independent variable is a powerful pedagogy, but not where the focus is a resource or a technology. For examples of such powerful pedagogies, take a look at the P&T book above or at the 2007 annual report from the National Survey of Student Engagement or reports from the Association of American Colleges and Universities.

Steve Ehrmann