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Smaller classes become big issue

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

In the past few years, the most persuasive piece of evidence in the class size debate has been a novel study by Harvard University's Caroline Hoxby. Instead of conducting a new experiment, Professor Hoxby adopted an ingenious research strategy, looking for a "natural experiment".

As in Australia, many US schools have a rule that when class sizes exceed a fixed number, another class will be created. For example, if class sizes were capped at 25 students, one school may have 50 students in second grade, yielding two classes each with 25 students, while a neighbouring school with 51 second-graders would have three much smaller classes. By examining many such natural experiments, Hoxby's study avoided distorting the regular incentives that teachers face.

The results of this study have turned the class size debate on its head. Basing her analysis on a large sample of Connecticut schools, Hoxby found that the effect of smaller class sizes was precisely nil.


This research supports the view enunciated last year by a spokesman for NSW Education Minister John Aquilina that "we are not aware of any current research which shows reducing class sizes significantly improves student outcomes".

This leaves us with something of a puzzle. Why don't smaller class sizes improve student performance?

The answer may lie in how teachers spend the extra time they have when class sizes are reduced. Consider an analogy. A doctor working in a hospital may be obliged to visit 25 patients per shift. If we required the doctor to visit only 20 patients instead, then either they will carry out better consultations or their patients will get the same attention but the doctor will feel less pressure. So it is with teaching.

Most likely, both effects will occur – lower class sizes will translate to some extent into better outcomes for students, while also contributing to a more comfortable life for teachers.

This may not be a bad thing – as the relative wages of teachers have fallen over recent decades, perhaps it is only fair that we ask them to do less. The key is to ensure that we get the balance right.

One thing Project Star successfully showed is that across-the-board reductions in class size will produce gains in student learning if teachers face strong incentives to produce better outcomes.


International evidence also teaches us that getting rid of the very largest classes is useful. In Israel, studies have shown major gains from getting classes closer to 30 than 40 students.

Yet the same does not necessarily hold for countries that already have smaller classes. According to the OECD, the average primary school pupil-teacher ratio is 19 in the US, 21 in England/Wales, 17 in Canada, 21 in Japan and 18 in Australia.

Doubt about the efficacy of across-the-board class size cuts should not deter education reformers from seeking innovative solutions to improving the quality of education. Better teacher training, fresh ways of improving teacher quality in poorer areas, remedial after-school programs, and targeted class cuts are all potentially effective ways of targeting resources where they will do most good.

The lesson of class size research is that policymakers should be modest enough to put reforms to the test, and flexible enough to adapt them in response.

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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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