The PISA results came out this month, and like most people in this industry I have spent more time with them than I meant to.
Let me say at the outset what this is not. It is not an analysis. There are people far better qualified than I am producing those, and by now you will have read several of them.
This is simply what I think after a week of turning the results over, and what I have not been able to put down since.
What I cannot put down is not the decline. The decline is real and it is serious.
Reading across the OECD has fallen by something close to a year and a half of learning since 2015.
Mathematics sits at the lowest level PISA has ever recorded.
One in five fifteen year olds across OECD countries is now below baseline proficiency in science, reading and mathematics at the same time, which was one in six only three years ago.
Nobody should wave any of that away, and I am not going to.
But our response to a PISA release is always the same, and it has been the same again.
We rank the countries.
We admire the systems at the top, we write commentary about the ones that slipped, ministers give interviews, and somebody produces a graph of the last twenty years.
Within a fortnight the conversation has finished and we go back to work until the next cycle.
In the middle of all that, there is a question I almost never hear anyone ask.
Who are the children behind these numbers, and does anybody actually know how they got there?
There is a figure in this year's results that I think deserves far more attention than it is going to receive.
Socio-economic background explains about twelve percent of the variation in science performance between students within a country.
Twelve percent.
Take two fifteen year olds in the same country. One outperforms the other.
The material circumstances they were born into account for roughly an eighth of the distance between them.
I want to handle that finding carefully, because it can be misused in both directions.
It does not mean disadvantage has no effect.
Advantaged students still outscored their disadvantaged classmates by a wide margin in every system, and the gap narrowed this cycle mainly because advantaged students did worse rather than because disadvantaged students did better, which is nobody's idea of progress.
But it does mean something that I think we skate over.
The overwhelming majority of the difference between one child and another is made of something else entirely.
So what is the something else?
That is the question I would want answered if I were running a school this month, and I would want it answered about my own students rather than about my country.
It is a far more useful question than where anyone placed in a table.
The something else is not mysterious.
Anyone who has worked in a school can name most of it without thinking very hard.
What motivates this child, and whether it is still the same thing that motivated her last year.
What she does when the work gets hard, whether she asks for help or goes quiet, because those two children need completely different responses and look identical on a mark sheet.
Where she learns well and where she does not, which is partly about the room and largely about who else is in it.
How she reasons, and whether the way we happen to teach suits the way she happens to think.
Her temperament.
Whether she feels she belongs in the building at all, which PISA does ask about and which very few schools ask about their own students.
What was going on at home during the term her attendance quietly slipped.
Whether the activity she loved in Year 7 is the one she stopped turning up to in Year 9, and whether a single adult noticed.
None of those things appeared in her score.
All of them produced it.
There is a smaller finding in this year's results that makes the same point from another angle.
PISA added a new domain this cycle, computational problem solving, and across OECD countries around two thirds of students reached the proficiency level that ma