There is a prevailing narrative around Scottish education that The Economist neatly summed up in a 2016 article: it was “once splendid” but has become “slightly shabby”. This description is less hyperbolic than a lot of criticism that Scottish education faces, but it still reflects the commonly held view that, after a long time leading the world in education, Scotland has now been reduced to an also-ran.

There is a tendency to overstate the achievements of the past and filter out current successes, and Scotland’s record in the Programme for International Student Assessment (Pisa) is invariably latched upon by those who do so. Last week, however, and not for the first time, concern was raised about the use of Pisa results as a yardstick for education systems (“More doubts cast on reliability of Pisa scores”, tes.com, bit.ly/PisaStudy).

Professor John Jerrim, of the University College London Institute of Education, looked at Pisa data from more than 3,000 students in three countries that take part in the study of 15-year-olds’ performance in maths, reading and science. Analysing the impact of a switch from paper to computer-based testing, he was not convinced by the efforts of the Organisation for Economic Cooperation and Development (OECD), which runs Pisa, to adjust results accordingly.

Jerrim said: “Could this have driven some of the more surprising findings from the Pisa 2015 study, such as Scotland’s plummeting performance on reading and science compared with 2012; the significant drop in science performance in Ireland and Germany compared with 2012; or the significant decline in several East Asian countries? I certainly don’t think we can currently rule out such possibilities.”

The point is not that Pisa should be dismissed out of hand, but that we should be wary of criticism of Scottish education that relies solely on Pisa to prove that it is failing.

Apportioning blame

Of course, the tendency for critics of the Scottish government’s education record to cite Pisa ad nauseam can, ironically, be blamed partially on the Scottish government, which several years ago withdrew Scotland from other international barometers of education, the Progress in International Reading Literacy Study (Pirls) and Trends in International Mathematics and Science Study (Timss).

And this year, there will be no new results from the Scottish Survey of Literacy and Numeracy, which the government has also scrapped.

In other words, when assessing the performance of Scottish education, it is no wonder that casual observers fixate on Pisa - because they don’t see much else to go on. As a result, Pisa is more likely than ever to set the agenda for Scottish education, no matter the doubts about the reliability of its findings.

One issue on which there seems no doubt that Scotland has a long, long way to go is LGBT pupils’ educational experiences: for many, school remains a gauntlet to be run.

Although the personal testimonies in the 2017 LGBT Youth Scotland survey of young people’s lives - its first since 2012 - are shocking enough, some of the stark statistics resonate just as much.

Nearly half of LGBT young people, for example, said their experience of school was “bad” (only 5 per cent of those who have been to college recalled it as bad, and 3 per cent of those who have been to university said that was bad). Bad is often a euphemism for traumatic: 41 per cent had suffered physical assaults in education settings.

At school, if you are LGBT, you cannot always just get on with your learning - too many young people feel they have to watch their back, and a significant minority say that bullying drives them away from education altogether. That’s a failing which, surely, we can all agree needs urgent fixing.

@Henry_Hepburn