The expert who described Scotland's performance in the last Pisa international tests as "treading water" now believes "Scotland can be proud of its education system."
Michael Davidson, a senior analyst with the Organisation for Economic Co- operation and Development (OECD), which is responsible for Pisa, told a gathering in Edinburgh: "Scotland's performance is good, but some countries are aiming to move from `good' to `great' and from `great' to `excellent'."
The three-yearly tests in reading, maths and science among 15-year-olds, administered in 2009 by Pisa (the Programme for International Student Assessment) in 74 countries and regions, produced Scottish results generally seen as average.
But Scottish Government analysis suggests that, after declining previously, performance was "relatively unchanged" between 2006 and 2009: above average in reading and science, and similar to average in maths.
Mr Davidson agreed that Scotland's showing had "stabilised" from 2006-09, but did not know why.
The results nonetheless provoked much heart-searching in Scotland and led to Education Secretary Michael Russell setting up a national working group on attainment.
He is determined to avoid any dubiety about the results from the 2012 tests, to be taken in around 110 Scottish secondary schools next March. The international results will be published in December 2013.
The analysis by Mr Davidson, a Scot from Perth, revealed a mixed bag of conclusions.
The Chinese province of Shanghai, for example, was top for all three subjects in 2009, scoring 556 points in reading, 600 in maths and 575 in maths (Scotland: 500, 499 and 514).
But Shanghai authorities had to take rigorous action. There had been a "huge variation" between schools' performance (in contrast to Scotland, where the greater variation is within schools), so Shanghai paired the best schools with the worst.
The region now claims to have turned the situation around in two years, with parents flocking back to the previously poor schools.
The commonest feature in improving countries was that considerable efforts had been put into tackling under-achievement - except in Korea where effective steps had been taken to raise overall performance (in reading), with the negative effect of widening the gap between successful and struggling learners.
Although much is made of the impact of pupils' backgrounds, the Pisa results found that only 14 per cent of variation in reading performance in Scotland could be explained by socio-economic factors - similar to the OECD average.
Scotland's particular challenge, Mr Davidson went on, lay in the relatively poor "resilience" of its pupils - a measure of those from poor backgrounds whose results were better than expected. The average OECD score was 31 per cent, while Scotland was at 28 per cent. Shanghai and Hong Kong had more than 70 per cent of resilient students, with Finland at 50 per cent.
One of the most striking statistics about Finland's system was that, by the time pupils were 15, around half would have received some form of special education. "In other words, they spot problems early and have good systems for dealing with them," he commented.
Mr Davidson, addressing a meeting convened by the Scotland China Education Network, reiterated the OECD view that well-paid and well-regarded teachers, allied to strong continuing professional development, was crucial.
But almost as important was "reading for enjoyment". This strongly related to school performance in Scotland, where 43 per cent of students did not read for pleasure, compared with 8 per cent in Shanghai.
Warning over global studies
A Cambridge University professor has laid out the perils of comparative international studies, writes Henry Hepburn.
Robin Alexander, speaking at the annual conference of the Scottish Educational Research Association, said that countries which did well in Pisa were usually small, rich, or both, such as Singapore and Hong Kong. He added that policy makers tended to react to Pisa by focusing on teachers, obscuring the impact of social inequality, gross domestic product and a country's size.
Professor Alexander, a past president of the British Association for International and Comparative Education, advised against copying policies or processes that were successful in another culture; re-examining underlying principles and values was more important.
He questioned whether, judged by criteria other than testing 15-year-olds at reading, maths and science, the top Pisa countries were genuinely world class for education.
Education should be driven by "international interdependence," he suggested, rather than "national supremacy". "Should world-class education be about beating the world or sustaining it?" he asked.