Had I been Scotland's only representative in the Programme for International Student Assessment (Pisa) all those years ago, a national scandal would have ensued.

Countless outraged words (not that I could have counted them) would have been devoted to the question of one youth's matchless ignorance in maths and the sciences.

I would have been able to read those words easily enough. In that area, I was fine. In due course, in consequence, it led to me being called educated. Put aside any doubts about the liberal arts and their contribution to human prosperity, therefore, and you might wonder what it is that Pisa is supposed to measure. "Reading", maths and science only: that narrows the field a bit.

This time around, Scotland has done better than the rest of Britain in this spurious triennial league table, but that isn't saying much. You can guarantee it won't have Michael Gove rushing to his homeland to discover what the Scots are doing right in maths and reading that he might have missed in his drive to turn English education upside down. Equally, it won't have new Labour confessing that its vaunted reforms down south, the ones that produced the 15-year-olds graded under Pisa, worked no miracles.

Scotland's relative success will also do nothing to deter those who fancy putting our pupils through Mr Gove's mill. They do a nice line in cherry-picked facts. They especially like to argue that the state serves the best-off Scottish youngsters best and the worst-off worst. The conclusion, rather than the assertion, is the problem. Somehow mobility through education for the selected few is preferred to ending inequalities for all. But those who take the view have a problem. It's called Finland.

That small northern country has become something of a cliche in education circles, but for the best of reasons. Contemplating Britain in mid-table in rankings dominated by Chinese cities, Korea, Singapore and Japan, our politicians talk a lot about the Finns and how, year on year, they meet the notional challenge from the east. Applying the lessons freely available is a different ideological matter, even when it is obvious that the success of the Chinese and Koreans is bought by turning millions of young people into miserable, enslaved wrecks.

Finland easily places in the top half dozen in the contest run by the Organisation for Economic Co-operation and Development (OECD). Britain, taken as a whole, lies outside the top 20 among 65 countries. We stand alongside the likes of France and Iceland, broadly "out-perform" Italy, the United States, Israel and Sweden, and lag behind New Zealand, Ireland, Australia, Germany and Canada. If Pisa is your criterion, you'd want your children educated in Finland, Estonia, the Netherlands or Switzerland. But what about these rankings? As observed, their yardsticks are limited indeed. Mr Gove with his 2:1 in English might have let the side down in this game. Tristram Hunt, the Labour shadow, is a historian, and therefore not quoted. Michael Russell, our own champion in education, did some theology before moving on to history and literature: another arts type in a world being shaped to the ends of productive industry by the OECD's attainment experts. They identify things that matter, but not every important thing.Ironically enough, however, most of the criticisms of Pisa have been levelled at precisely the leg of the testing tripod liable to support the claims of non-scientists.

Many have wondered just how you measure and rank attainment in reading when so many different languages and cultural assumptions are involved. Reportedly, the OECD has attempted to compensate statistically for the difficulties, but that's not exactly reassuring. You begin to wonder if something equivalent to Boris Johnson's idiotic application of IQ testing is at work.

But let's make no excuses. Whatever the differences within Britain, the OECD reckons the country is marking time, barely improving on its showing in science (20th), reading (23rd) and maths (26th) since 2009. The latest scores are, accordingly, 514, 499 and 494, with Scotland registering 513, 506 and 498. That's not catastrophic, but it wouldn't get you to the group stages. More importantly, according to numerous observers, it masks profound inequalities.

Yesterday, Andreas Schleicher, the OECD deputy director for education and skills and the co-ordinator of Pisa, said the data "doesn't show much of a performance difference between public and private schools, once you account for socio-economic background". This is also true in the state sector. As proponents of reform often observe, Britain's middling performance is due to averages. The best state pupils do as well as any in the world; the worst, the least advantaged, drag the rankings down.

If the vaunted educated workforce trained to compete in the international jobs market is what matters, then, Britain's neglect of inequality is utterly self-destructive. In this contest, a tolerance for poverty matters more than another grand scheme to reform an education system to bits. That doesn't mean that reforms are not needed. But the perpetuation of inequality through the school system is a strange way to achieve anyone's ambitions for the young.

So what about that Finnish model? According to the OECD, it has resulted in "grades" of 545 in science, 524 in reading, and 518 in maths. Those have been achieved by a publicly-funded comprehensive system that doesn't bother with school uniforms, selection, tracking or streaming. In higher education, a four-year trial of tuition fees has led the main universities to decides that such imposts, for domestic or foreign students, amounts to a very bad idea.

Finnish schools are local, whenever possible, and granted a great deal of autonomy. They are blessed with teachers whose training, status and pay are beyond the imaginations of the average British politician. To teach in Finland you must survive tough competition and possess a master's degree. Your reward is a wage well above the OECD average and a great deal of public respect. There is no shortage of applicants for teaching jobs. Demand outstrips supply.

The Finns have slipped a bit on the Pisa rankings. They are no longer top and this is as controversial in Helsinki as Britain's showing is in London or Edinburgh. But Finland does not bother with the pretence that "reform" is a substitute for public spending on education; nor does it believe selection for the few is of any great use to the country as a whole. The results speak for themselves.

So why not just adopt the Finnish system for the nations and regions of Britain? In England, the Tory delight in privatisation would prove an obstruction. Private schools and their customers would grow uncomfortable with the idea that advantage could no longer be bought in the face of an authentic publicly-funded comprehensive system.

We already know why some youngsters in Britain excel. We know with equal certainty why some do not. The deepest educational failure has been among politicians.