Richard Teese's letter of April 11 about inequalities of attainment in Scottish schools is welcome, especially his emphasis that the most valid criteria for any country are based on its own systems of assessment.
Professor Teese also points to the equally important matter of social- class inequality. Assessing the relative size of this raises rather complex methodological issues.
The Organisation for Economic Co-operation and Development report on Scottish schools reaches its pessimistic judgment on inequality mainly on one measure: the percentage of the total variation in attainment that is explained by socio-economic status (SES). But this percentage is a product of two things: the strength of the relationship between SES and attainment (the "slope"), and the total variation in attainment that is to be explained.
The slope is what we should really be interested in: it shows the difference between expected attainment among low-SES and high-SES pupils.
In Scotland, the total variation is relatively low, the slope is also quite shallow (ie low inequality), and so the proportion of the total variation which is explained by SES is quite large by international standards.
For example, in the 2003 Programme for International Student Assessment study, the Scottish slope in mathematics was notably shallower than the OECD average, and was steeper to a statistically significant extent only than in Canada, Finland, Iceland, Luxembourg, Mexico, Portugal and Spain. These last four had much lower attainment than Scotland at all points in the SES distribution, and Iceland had lower attainment among high-SES pupils.
So, on the combined criteria of high equity and high attainment - which Professor Teese in his letter rightly invokes - Scotland was bettered by only two countries. Reading and science showed much the same patterns as maths, but science was somewhat less favourable to Scotland.
Scottish education will always need to improve. But if we want to do better, we will have to look at the best performers internationally, as The TESS has been doing in its admirable series on Finland. Professor Teese's report advises exactly that, but the problem is that commentary upon it has concentrated on deficiencies rather than building on achievements.
Lindsay Paterson, Moray House school of education, University of Edinburgh.