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Smaller classes become big issue

By Andrew Leigh and Justin Wolfers - posted Saturday, 15 June 2002

Student-teacher ratios are going to be a major issue in 2003, especially in NSW, where the Primary Principals Association and Teachers Federation have launched campaigns for reduced class sizes. But are the would-be reformers right that "Twenty is Plenty"?

It is almost certainly true that smaller class sizes will make classroom life more pleasant for teachers, and probably also our children. But the more important question is whether there will be any educational benefit. Unfortunately, research on this question is scantier than most advocates seem willing to admit.

This arises because small classes tend to appear in two contexts – in rural Australia or in rich private schools. Comparing the outcomes in these settings with larger classes found in suburban public schools risks comparing apples with oranges.


Moreover, comparisons within a school are not much better.

Principals often tend to use small classes as a means of either enriching gifted students or remedying disadvantage among at-risk students. Thus, comparisons of the performance of small and large classes may obscure more than they reveal.

In the absence of any good Australian experimental evidence, both advocates and sceptics have drawn – often selectively – from American research. But until very recently, most of this research has been of poor quality.

An influential review by Stanford's Eric Hanushek concluded that it is hard to find any effect of class size on student achievement. But while this militates against across-the-board reductions in class size, Hanushek argues that there probably are gains from reducing student numbers in specific circumstances – such as for disadvantaged and at-risk youth.

This is where the debate rested until the results from Project Star materialised.

One of the largest education policy experiments ever conducted, Project Star cut class sizes in a randomly selected group of Tennessee schools. Students from these schools were then compared with a control group who had experienced no such reduction in student-teacher ratios. When follow-up studies were conducted, Princeton's Alan Krueger and collaborators concluded that test scores of those in smaller classes had indeed improved by a substantial margin, relative to those in larger classes.


Patricia Forsythe, the NSW Shadow Minister for Education, has claimed lately to have been following the US evidence closely. Presumably Project Star underpins her claim that "the weight of evidence in relation to smaller class sizes for the beginning years of school seems to be compelling." But is Project Star compelling?

The sceptics doubt it. Social science has long known about the "Hawthorne effect" – the tendency of subjects to alter their behaviour when they know they are being observed. Thanks to a prior agreement with the Tennessee education union, teachers in the schools with smaller classes knew that if their students performed well, class sizes would be reduced statewide. If not, they would return to their earlier levels.

In other words, Project Star's teachers had a powerful incentive to improve student performance that would not exist under ordinary circumstances.

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This article was first published in The Weekend Australian on 1 June 2002.

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About the Authors

Andrew Leigh is the member for Fraser (ACT). Prior to his election in 2010, he was a professor in the Research School of Economics at the Australian National University, and has previously worked as associate to Justice Michael Kirby of the High Court of Australia, a lawyer for Clifford Chance (London), and a researcher for the Progressive Policy Institute (Washington DC). He holds a PhD from Harvard University and has published three books and over 50 journal articles. His books include Disconnected (2010), Battlers and Billionaires (2013) and The Economics of Just About Everything (2014).

Dr Justin Wolfers is an Assistant Professor of Economics at Business and Public Policy Department of the Wharton School, University of Pennsylvania.

Other articles by these Authors

All articles by Andrew Leigh
All articles by Justin Wolfers
Related Links
Andrew Leigh's home page
Justin Wolfers's home page
Kennedy School of Government, Harvard University
Stanford Business School
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