MEMBERS of John Swinney's panel of world leading education experts have said cutting class sizes in Scotland would make little difference to achievement in schools and would be hugely expensive.

Dr Avis Glaze, a member of the Scottish Government's international council of education advisers, warned that "changes in class size are one of the most expensive changes possible" due to the need to build new classrooms and staffing costs.

The Canadian-based international expert on education insisted she was not speaking "as a member of the international advisory council" that Swinney, the education secretary, appointed her to but from a "personal and private perspective".

However, Glaze, who has advised governments around the world and is a renowned author on education, suggested “teaching competence and leadership effectiveness” were a higher priority than reducing class sizes.

Dr Pasi Sahlberg, a visiting professor at Harvard University who is also a member of the government's panel of 10 experts, suggested that “reducing class size has only a small (positive) impact” on delivering education improvement.

The stark claims were made as the Sunday Herald today looks at whether smaller class sizes change educational outcomes in our latest State of the Nation investigation.

Pupil teacher-ratio in schools has been an issue the SNP government has been repeatedly challenged on since the party came to power in 2007 on a manifesto that included a pledge to "reduce class sizes in primary 1, 2 and 3 to 18 pupils or less to give children more time with their teacher at this vital stage of their development".

However, Glaze, who has served as education adviser to governments such as New Zealand and Ontario in Canada, said that class size "does very badly in terms of 'value for money' comparison" and suggested the money would be better spent elsewhere.

She said: "Class size has been and continues to be one of the controversial issues in education. People have strong views on this – both from what the research says and from anecdotal, personal experiences.

"The research is clear that small reductions in class size (e.g. from 25 students to 20 students) do not appear to have any effect on student outcomes, perhaps because teaching practices don't change in those cases.

"Teachers, of course, have a strong preference for small classes, especially when they have to deal with children with many challenges that must be addressed in their classrooms, while they work valiantly to address the government mandates and high expectations...Large reductions in class size (e.g. to below 15) might, based on the evidence, make a significant difference in outcomes."

She added: "However changes in class size are one of the most expensive changes possible, since they involve not only huge operating cost increases but also, in most cases (as in Ontario when we were there) large capital costs for additional classrooms.

"Class size does very badly in terms of 'value for money' comparisons of various education interventions. It appears that you can get far more impact from a similar expenditure if it's used for other things. In all of these debates we should not forget what the research says about two of the innovations that do have an impact: a focus on teaching competence and leadership effectiveness. Spending our rapidly depleting resources on capacity building in these two areas will make a difference."

Meanwhile, Sahlberg, a Finnish education guru, said that smaller class sizes could potentially benefit younger school children.

He said: "In general, research from around the world has concluded that reducing class size has only a small (positive) impact on student achievement in school.

"There is also good amount of research that suggest that smaller class sizes benefit much more children in primary school than in upper grades.

"My personal opinion is that if you can afford reducing number of kids in classrooms you should do that in pre-school and in first four grades of primary school, especially in schools that cater children from more disadvantaged circumstances. Later the intended affects are much more unlikely.”

However, Professor Christopher Chapman, chair in educational policy and practice at the University of Glasgow's Robert Owen Centre, suggested smaller class sizes could have some benefit if the policy was targeted at the less well off.

He said: "It's contested ground, but there's some evidence that suggests class sizes does matter. It's an expensive strategy. To reduce class sizes from 30 to the 20s is tinkering at the edges. There's evidence that reducing class sizes to a figure below 18 and focussing on children from disadvantaged backgrounds could work."