Plotting a graph of Scottish pupils' performance in the international studies run by the Organisation for Economic Co-operation and Development would reveal a very mixed performance against the other countries that participated, ranging from good through mediocre to poor.
However, it would be unwise to read too much into these studies for a number of reasons. None of the organisations conducting them used directly comparable methods or even samples. In some countries, the samples are small. This, combined with the infrequency of the studies, makes them statistically unreliable.
As with domestic studies, these do not reflect on the performance of current governments but on the policies of several years previously.
The Programme for International Student Assessment (PISA) studies are particularly difficult to interpret, because the surveys are designed to measure the attributes of children of a certain age, rather than the performance of schools.
It includes pupils from private schools. In many countries, the distinction between private and state schools is much less stark than here, but presumably the inclusion of private schools, which perform better than state schools in Scotland on most measures, improves Scotland's PISA performance.
By contrast, in Scotland pupils from special schools were not included, unlike in other countries such as Germany.
The survey measures pupils' "life skills", not the performance of schools in teaching a curriculum. Many cultural influences from outwith school affect the results (it is particularly noticeable that English-speaking countries tend to do well).
Being age-based, the survey suits those education systems, such as Scotland's, where pupils of a certain age are, by and large, in the same grade.
Although PISA is not a measure of Scottish state school performance, it is clear that our performance, along with others in the study, has not improved over time. This is despite the big spending increases in preceding years - to the point where spending per head on education in Scotland is at least 10 per cent above the OECD average. Reliance on the small sample used in the PISA studies alone is liable to lead to misplaced complacency by our policy-makers.
Instead, they should focus on exam results, which give a much more comprehensive picture for measuring the state school system. The number of children getting five good grades at S4, including maths and English, should now become the official benchmark.
Scotland needs to move out of its comfort zone and set a detailed, long-term plan of how it intends to double attainment. This should include how long the process will take, how much it will cost and how it will be funded.
If politicians intend to maintain their control over education, then the people who pay for it deserve some detailed information on the long-term plans for improving matters.
James Stanfield is a research associate at the EG West Centre at the School of Education, University of Newcastle upon Tyne.