Given that class size reduction is a key (and costly) component of many school reform efforts, I'm happy to see that it's being studied extensively. In the past few weeks, we've looked at a study from Kenya that showed that class size reduction is most effective when accompanied by ability grouping, and a rehash of the Tennessee STAR study that found that smaller classes benefit higher-achieving students more than lower-achieving students.
Now, a new study looking at schools in four countries (US, UK, Hong Kong and Switzerland) asks another question. If we assume that small classes are better for kids (which, I want to stress again, has not been proved conclusively -- it is very hard to isolate variables), why would we suppose that would be? Is it because teachers teach differently when they have smaller classes? Or is it because students behave differently in small classes?
According to research presented at the American Education Research Association conference in late March (and written up in this article in USA Today), it's not the former. In small classes, many teachers continue to teach as though they still have a large class. They make presentations that don't necessarily involve the students; they don't demonstrate what the students themselves will then do. But the students themselves spend more time on task. It seems that teachers are better able to maintain control in smaller classes, and so more time is spent on learning, and the students are able to spend more time engaged with the teacher than they are in larger classes.
It's a tricky issue. Perhaps if teachers were trained to better leverage their smaller classes, then small classes would result in more benefits. But it's hard to know. The article notes that in two of the four countries studied, the results were inconclusive. Indeed, some countries with the best academic results have the largest classes! This article (and chart, about halfway down) shows that while we quibble over whether classes have 20 or 25 pupils, in South Korea, Singapore, Hong Kong and Japan (high scorers all), class size averages over 30 students.
My own opinion? From what I've seen of various studies, I'm currently thinking that teacher quality and (much harder to control) student quality matter most. By "student quality" I mean kids coming to school ready to learn, well-fed, well-rested and safe, and firmly ensconced in a culture that values education. After that, ability grouping is probably the most important factor. After that, class size. So yes, we can spend billions to make classes smaller. But paying brilliant teachers $150,000 a year and removing any teacher who can't keep up is probably a better idea, even if it means class sizes of 30 or more.