Sunday, July 27, 2008

Sunday dollars+sense: We are being offered lower class sizes


There isn’t a parent, there isn’t a teacher, who wouldn’t like lower school class sizes.

The ACT Opposition is counting on it.

At a cost that will eventually climb to $14 million per year they are promising to cut the size of every government primary school class to 21.

All that’s missing is the money and the evidence.

Put another way, what’s missing is evidence that cutting the class sizes would be value for money.

The concept of “value for money” is hard to grasp when you are an anxious parent (like me) being offered a gift during an election campaign...

It only makes sense if you compare it to the value that could be got if the $14 million per year was spent in another way.

It could be spent on salary bonuses for teachers who are really good. An extra $10,000 or an extra $20,000 per year might keep and attract the teachers that we really need as well as fostering a culture of excellence.

The Liberals say they’ve got evidence that lower class sizes would improve educational outcomes. But it is so weak as to be embarrassing.

Quoted with approval in their policy document, it a study undertaken for the NSW government that asked parents, principals and teachers “whether they thought the class size reduction had had an impact upon student attainment in literacy and numeracy”.

Guess what? They did. But there was no objective measure in the study of whether those outcomes had improved and the answers received were a bit like those you would expect to a question phased along the lines of, “we have just spent more money on you – has it helped?”

Lower class sizes often seem to help. We see them in special classes for poorly-performing students and for gifted children. But that doesn’t mean they help generally.

Project Star in the United States was the biggest attempt to answer the question. It cut class sizes in a randomly selected group of Tennessee schools and then compared the results of their students to the results of those in schools whose class-sizes hadn’t been cut.

The results were impressive, but tainted.

The teachers knew about the trial and knew that if it succeeded class sizes would be cut statewide.

Andrew Leigh of the ANU points to a better more recent study by Harvard University's Professor Caroline Hoxby who compared the results of students in classes that just happened to be large with those that just happened to be small.

As he puts it, her massive study found the effect of class size on performance to be “precisely nil”.

So we won’t miss out on much if the Liberals don’t win.


Canberra Liberals,
First Class Education Policy, July 2008.

Bob Meyenn,
Class size pilot evaluation report, NSW Department of Education and Training, 2003

Krueger and Whitmore,
Student/Teacher Achievement Ratio (STAR) study, Tennessee Department of Education, 2001

Caroline M. Hoxby, "
The Effects of Class Size and Composition on Student Achievement: New Evidence from Natural Population Variation," NBER Working Paper 6869, National Bureau of Economic Research, 1998

Andrew Leigh and Justin Wolfers,
Smaller classes become big issue, June 2002

ACT Council of Parents & Citizens Associations,
Research Findings on Class Size Reductions, 2005

Ludger Wößmann, Martin R. West, Class-Size Effects in School Systems Around the World: Evidence from Between-Grade Variation in TIMSS, March 26, 2002

Peter Martin, Lessons must be learnt if we are to keep teachers, Sydney Morning Herald, January 12, 2005

Peter Martin, Paying teachers for performance, Canberra Times, March 5, 2007


Anonymous said...

Class-Size Effects in School Systems Around the World


We estimate the effect of class size on student performance in 18 countries, combining school fixed effects and instrumental variables to identify random class-size variation between two adjacent grades within individual schools.


Smaller classes exhibit beneficial effects only in countries with relatively low teacher salaries. While we find sizable beneficial effects of smaller classes in Greece and Iceland, the possibility of even small effects is rejected in Japan and Singapore. In 11 countries, we rule out large class-size effects.

Peter said...

Dear A,


I've added it to the list of references. Peter

Grog said...


You've got a bit of a typo: is it $14 million (I presume so) or $14 billion?

Peter said...

Dear g,

Thanks. I've fixed it. P

LETTERS said...

Letter to the Editor, July 31, 2008

Peter Martin's assertions (''The question of size is academic'', July 29, p30) that smaller class sizes don't deliver better education is an unfortunate example of economists claiming to know more about complex issues than than the experts.

He states that the outcome of experiments on smaller class sizes is unavoidably biased and unreliable. But then we could equally well say this about tests on larger class sizes.

Therefore, since no evidence either way can be accepted (at least by economists), we should prefer larger class sizes on cost grounds alone.

It is odd, then, that Martin, as an economist, does not discuss what the optimum size is. Is it 100, 200, 1000 or some value remote from common sense?

Nor does he mention such obvious externalities as teacher retention rates and student-teacher relationships.

David Roth, Kambah

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