Scotland is closing the gap between its highest and lowest achievers in maths and reading, the latest figures from the Organisation for Economic Co-operation and Development show.
The OECD's Programme for International Student Assessment (Pisa) examines young people's ability to use their knowledge and skills to meet real-life challenges rather than whether they have mastered a specific curriculum.
It found Scottish pupils scored particularly well in "uncertainty" (only the Netherlands did better): the area of probability and statistics. Pisa regards understanding statistical ideas and the ability to follow statistical arguments as of increasing importance, if citizens are fully to participate in democratically organised societies.
In another area of maths, "change and relationships", which relates most closely to algebra, only Korea and the Netherlands did better than Scotland.
However, in the other two content areas, "space and shape" (geometry) and quantity (aspects of maths dealing with number), Scottish performance was good but not strong. In space and shape, 13 countries had higher mean scores, nine significantly so, and in quantity, eight countries had higher mean scores, five significantly so.
The analysis report for the Scottish Executive on Scotland's performance in Pisa was carried out by Graham Thorpe, who recently retired from the Scottish Council for Research in Education Centre.
Reading literacy as defined in Pisa focuses on students' ability to use written information in various situations.
In the whole of the OECD area, 8 per cent of students were found to be proficient at level 5, the highest level. The top performer was New Zealand with 16 per cent, with Scotland at 9 per cent.
However, only the three top performing OECD countries on the Pisa 2003 reading literacy scale (Finland, Korea and Canada) had mean reading scores significantly higher than that of Scotland.
Comparison between 2000 and 2003 showed that Scottish students in the two lowest ability groups in reading improved their scores by nine scale points but that scores for the third group have not changed appreciably. In all the OECD areas, the performance of students at such levels has fallen.
However, Scotland's mean score for literacy fell by 11 points between 2000 and 2003 - a decline largely attributable to lower performance by pupils at the upper end of the ability range. "These differences are statistically significant," the Scottish report states.
In scientific literacy, the Pisa study found only Finland, Japan and Korea had significantly higher mean scores than Scotland.
On the equity scale - the gap between the low and high achievers - Scotland's rating was neither particularly good nor bad.
However, the SCRE report states, both in respect of quality, as measured by the overall mean score, and equity, as measured by the differences, Scotland falls well below what can be achieved in a country such as Finland - top performer in the three subject areas.