There is a blight upon the Johnson household this year, as there has been for the past four years and as there will be for the next three. It is a blight that affects millions of households across the country at this time every year. It is exam season. The oldest finished his A levels two years ago, the middle one is doing his now. The twins do their GCSEs next year. In three years and a month it will all be over. I hope.

There is an additional blight upon us this year — the blight of the World Cup. As a non-football fan (there, I’ve admitted it), the World Cup generally pretty much passes me by. But I am, I realise, odd. It doesn’t pass by your average 16 or 18-year-old, and especially not your average 16 or 18-year-old boy, no matter whether they have exams to revise for.

And, as ever, the World Cup happens bang in the middle of exam season. Or to be less parochial perhaps I should say that exams happen bang in the middle of the World Cup. Whichever. The first game is the day before son number two has one of his computer science exams. The first England game is the day before one of his maths A-level papers.

This matters. Just as some economists in the US this week reported that hot weather lowers exam results, so researchers in Bristol and Oxford have shown that exam results in England go down during World Cup years. They go down especially for boys, and especially for boys from disadvantaged backgrounds. For the most affected group, the boys from poorer backgrounds, taking GCSEs in a World Cup year could reduce grades by as much as a third of a grade per subject. That’s big. Having a really good teacher as opposed to a not very good one has a similar scale of effect.

As the authors of that work point out this is, if nothing else, pretty good evidence of the importance of putting in the effort, including last-minute effort, for passing exams. An important message, if not an easy one to impart to recalcitrant teenagers, especially not when there are additional distractions available.

The fact that poorer boys are most affected is particularly concerning because they are exactly the group who do least well out of the education system. In fact, boys in general lag a huge distance behind girls. Last year 71 per cent of GCSE entries by girls were graded C or above (4 or above on the new scales) compared with 61.5 per cent for boys. That is an enormous difference and in some important subjects, such as English Language, the differences are much bigger still. Girls are nearly 25 per cent more likely than boys to get a C or above and are twice as likely as boys to get an A or above. These differences follow through into A levels and into university entry. Girls are more than 30 per cent more likely than boys to go on to university.

This isn’t because boys are less intelligent than girls. Clearly there are no economic or social differences. And this is not new. The gap has been there, and growing, for a long time. It was there when I left the Department for Education nearly 14 years ago. I thought then that it was one of the two or three biggest challenges facing the education system. So it remains. We rightly worry about the gender pay gap; we should also worry about the gender gap in our education system.

We should also worry about our rather odd exam system. To have high stakes national exams at the age of 16 — GCSEs — is relatively unusual by international standards. It is easy to understand their history: most young people used to leave school at 16, and some measure of attainment at that point made sense. Few now leave at 16. All are supposed to be in some form of education until they are 18. GCSEs have become just one more sorting mechanism. And as some recent work by economists at the London School of Economics has demonstrated, they sort in a way that can be really quite damaging.

Using data on the precise marks that students got at GCSE English, the researchers were able to look at the impact of just getting a C grade as opposed to just missing a C grade — literally the impact of getting a single additional mark. The results are disturbing.

Missing a C grade in English language by a tiny fraction decreases the probability of enrolling in a higher-level qualification by at least 9 percentage points, with a similar effect on the probability of getting A levels or equivalent by the age of 19. This in turn affects the chances of getting into university and of getting a job with decent progression prospects, and so on. All for the want of a single mark in a single exam aged 16.

That this matters so much is barmy. It is a symptomatic of a much wider failure in our education system. A well-functioning system would provide support and opportunities for marginal students such as these rather than denying them opportunity. The educational options after 16 for those who are not successful at 16 are too few, too ineffective and too constraining.

But given where we are, the moral is clear. So come on boys. Turn off the TV, ignore the football, put your phone away and buckle down. Your future really could depend on it.