The administration of Donald Tsang Yam-kuen introduced small-class teaching in Hong Kong's primary schools several years ago, yet the current government seems to be resisting the same approach in secondary schools.
If reducing class size for primary students is a good thing, why is it not also good for secondary students?
For over 30 years I have been interested in the evidence about the effects of class size. Over that time, there has been little agreement on them.
Teachers in general feel that small classes are beneficial for teaching and learning because they realise the benefits of reorganising their teaching in a different classroom context. Yet economists and some educational researchers have argued class size is unimportant.
One argument has been that the expenditure on introducing smaller classes has little economic benefit. Another is the apparent lack of evidence for improved learning by students.
The views of economists and researchers may well account for the government's reluctance to reduce class sizes in Hong Kong's secondary schools. But what is the evidence for such views?
One source of evidence is the results of international assessments such as the Programme of International Student Assessment (PISA). Students in the education systems of East Asia do very well in such assessments and in general these systems have relatively large classes. Thus it is concluded that class size is not important to academic achievement.
Yet this argument is flawed, since it cannot tell us about the causal relationship between class size and academic performance. As a number of people have argued, there are a host of reasons why high-performing education systems such as Hong Kong's do well, including high levels of parental support, cultural factors that favour education and the prevalence of private tutoring, and so on.
Some educational researchers take a different approach to the issue, one that is often based on a large-scale statistical analysis of multiple studies related to the effects of class size. The conclusions have generally been that class size does not seem to have a large influence on student learning.
Yet, often, these analyses can include studies of varying quality, age of pupil, research design and so on. It is the same with the studies of many economists who measure class size and develop models of effects that bear little relationship to what actually happens in schools. Therefore, the results should be questioned, even though they may appeal to governments.
These two kinds of studies have been influential in suggesting that class size reductions are less effective than other, alternative interventions.
Of course, reducing class size in itself is not an educational intervention in the same way as one-to-one tutoring, peer tutoring or computer-assisted learning. Reductions in class size by themselves may mean very little unless they are accompanied by changes in teaching and classroom practice.
The benefit of reducing class size is that it allows teachers to alter the way they teach, the way they interact with students and they way they can support students. Researching class size reductions without also researching these changes to teaching practices only provides part of the research evidence.
Research I have conducted with my colleagues in Britain has shown some real benefits of class size reductions. We have shown that small classes are beneficial for young children and that the targeted use of small classes with low-achieving pupils and those with special educational needs would be beneficial at secondary level.
The benefits for these students have been shown to be real and sustainable. We have also found that the use of teaching assistants to help pupils with special educational needs is not a good substitute for teachers - indeed it can separate these pupils from the high-quality teaching they need.
Donald Tsang's government made a real step forward with its 2009 initiative reducing class sizes in primary schools. The current government can do the same by focusing on secondary schools.
Reductions need not be across the board if the costs in the first instance seem prohibitive. Yet if low-achieving students can be helped with smaller classes, more teacher attention and more engaging teaching strategies, then the benefits to Hong Kong are obvious. Similarly, if students with special educational needs can be helped with smaller classrooms, better teaching and more direct support, then again the benefits are obvious.
Governments have a responsibility to all students - not just the higher achieving ones. Leung Chun-ying's government can make a difference on this issue, and create a world first, by recognising the benefits of small-class teaching for those students in Hong Kong's secondary schools who will benefit most.
Peter Blatchford is professor of psychology and education at the Institute of Education, University of London, and visiting professor at the Hong Kong Institute of Education