The government's plans to reduce P1-3 class sizes came under renewed attack last week as the Parliament's education committee began an inquiry into the policy.
Directors of education argued against such an "ambitious national target" when there was a question mark over whether essential services could be afforded. And some of the UK's top research experts declared that, since teachers did not change the way they taught to match smaller classes, the policy did not achieve its potential.
But education directors saw no reason to provide training targeted at teachers of smaller classes, insisting that continuing professional development was as effective for smaller classes as for larger ones.
Leading the charge for greater local flexibility, John Stodter, general secretary of the Association of Directors of Education in Scotland, said: "The key requirement is that sufficient class-committed teachers are dedicated to P1-3 stages in each school to achieve an overall teacher- pupil ratio of 1:18.
"The class structure and deployment of staff would be for local decision by the headteacher, taking account of the educational needs of individual children and groups; the availability of accommodation; legislative requirements; teachers' terms and conditions; and any relevant education authority policies."
Terry Lanagan, director of education for West Dunbartonshire, described the policy of cutting P1-3 classes to a maximum of 18 as a "blunderbuss", which "unfortunately, some people think of as one loaded with a golden bullet". He asked MSPs: "Would you rather your child was being taught in a class of 18 by one teacher with no additional help, or in a class of 25 with a range of others coming in, such as learning assistants, early intervention teachers or network support?
"To say that, per se, reducing class sizes will improve attainment is very simplistic. It would be good to see a recognition that the level of support being put into supporting children is important, rather than simply a pupil-teacher ratio."
The committee had also called for evidence on the impact of smaller class sizes from some of the UK's leading experts on the subject.
Peter Tymms, professor of education at Durham University, said: "The gains from halving class sizes are not large, and there is a suggestion that teachers do not adjust their teaching as much as might be expected when they get smaller classes; they tend to teach in the same way."
He added that effective teachers produced bigger gains than modest class- size reductions. "If class sizes were reduced dramatically, many more teachers would be needed - but would they be as good as the existing ones? Probably not, on average," he said.
Maurice Galton, professor of education at Cambridge University's faculty of education, reached similar conclusions. "Against expectations, smaller classes do not result in individual pupils receiving more teacher attention on matters relating to task," he said. "There is little evidence that teachers change the way they teach in responding to class size reductions."
In developed countries, the main reasons that pupils' test scores improved in smaller classes was due to improved behaviour, as teachers spent less time exercising control of the class and more time teaching.
"But the gains are relatively small and not sustained over time as pupils move up the primary school," Professor Galton said.
He concluded that the potential benefits of smaller classes were not often realised: "There is a strong argument for stating that greater academic progress would result if teachers made greater use of teaching strategies which research has shown lead to improved performance."
The wrong formula?
The committee also heard a clash of evidence from leaders on whether the Government's proposal to extend pre-five education from 12.5 hours per week to 15 had any educational merit.
Andrew Sutherland, head of education services at East Ayrshire, and Jim Gilhooly, depute director of education at South Lanarkshire, welcomed the move to allow councils to target money set aside for increasing nursery education hours on reducing P1-3 classes instead.
But Maureen McKenna, head of education services in Glasgow, said the more time available for early intervention, the better, in the case of children from the most deprived backgrounds.
She also took issue with the formula worked out between Education Secretary Michael Russell and the Convention of Scottish Local Authorities, allowing councils to provide free school meals for only the 20 per cent most deprived areas in their authority.
It did not allow for the fact that Aberdeen had only 10 per cent of pupils in the most deprived top 10 areas; Inverclyde had 24 per cent and Glasgow 45 per cent, she said.
"Aberdeen will have to go up to the third decile to meet that 20 per cent target. Is that really the intention?" Ms McKenna said.