Scotland is "stagnating" compared to many other countries in the latest international survey of school performance, a leading expert claims.
Pupils are ranked as average for reading and maths and just above average for science, according to the 2009 findings from the Programme for International Student Assessment (Pisa). It has made no real progress since the last study three years ago, and has dropped closer to the average since the 2000 results when pupils' attainment was 5.6 per cent above the average for reading compared with 1.4 per cent last year; in science, it fell from 4.4 per cent to 2.6 per cent above.
Of the 65 school systems which took part in the survey, Scotland was in joint 15th place for reading, 12th for maths and 15th for science.
Despite this, the findings were hailed by Education Secretary Michael Russell as a sign that the "tide had turned", as the figures showed the previous slide in performance had been halted.
But Michael Davidson, a senior education analyst with the Organisation for Economic Co-operation and Development (OECD), which carried out the survey, interpreted the figures differently. "Scotland seems to be treading water," he suggested. "Its performance is around average. The question is - is average good enough?"
Lindsay Paterson, professor of educational policy at Edinburgh University, saw the figures as a sign that Scotland had stagnated or even fallen back.
"But that is also true of other similar countries with which Scotland is sometimes compared," he said.
In the other UK countries, Wales's performance dipped badly, while England and Northern Ireland hovered around the OECD average.
The most staggering finding is how well Asian pupils perform: the top five education systems are Shanghai province in China, South Korea, Finland, Hong Kong and Singapore.
Mr Davidson said: "Countries that have made advances have tackled issues vigorously. In Scotland, around 16 per cent of 15-year-olds are struggling in reading. Scottish education appears to be standing still, despite significant spending and reforms over the last 10 years."
The Pisa report suggested that success seemed to be linked to teacher pay and quality, rather than small classes. This was seized on by the Educational Institute of Scotland, whose general secretary, Ronnie Smith, said: "If Scotland is to progress, it is essential that our teachers are paid appropriately for the job they do, especially at a time of major curricular change."