Being a parent has its ups and downs. Being a father to four sons of very varying characters can also offer what are euphemistically termed learning opportunities. You can study the English education system as much as you like, as I have off and on since working at the Department for Education in the early 2000s, but it’s not until you experience some of its vagaries that you really begin to get a feel for the problems.

For my oldest son it all went rather well. Now 20, his path has been smooth. He had all sorts of options at the age of 11, attended a highly selective state grammar school, and is now at one the country’s foremost universities.

My second son, not so much. He had no choices at 11, and at 16 was not even welcome in the sixth form of our local so-called comprehensive. He is now in the second year of his A levels at a sixth form college. It really does seem to be doing a great job with a mixed bag of students. That would fit with wider evidence that sixth form colleges offer a pretty effective route. Along with all other sixth form and FE colleges, though, it has been starved of funding on a scale far beyond anything experienced by schools. The neglect of this sector, in both funding and public debate, is extraordinary.

It is at this point in the education journey, though, that the difference between the paths open to my sons really becomes apparent. For son number one it was easy. Go from great A levels into a great university. Son number two has also applied to universities. But even this is harder for those with weaker academic credentials. While the university application process itself is pretty straightforward, it is much harder to discern which courses are genuinely worthwhile.

But all that is a doddle compared with the alternatives. An apprenticeship looks like a good option for son number two. The government is promoting this as an alternative route. So I spent a large part of the Christmas holidays helping him to apply for higher and degree level apprenticeships. It is staggeringly hard even to find the right opportunities. As this newspaper reported last year, just 1,800 18-year-old school leavers started any form of higher apprenticeship in 2016. That’s an absurdly small number.

My son wants to be a computer programmer or software developer. Apparently this is a shortage occupation. You wouldn’t know it from the scarcity of openings. By comparison there are hundreds of relevant degree courses, all clearly advertised. In addition, apprenticeship applications tend to be far more complex than the Ucas application process, which gives you access to the whole university system. Many appear to be barely edited versions of the graduate application process — hardly encouraging, or suitable, for the average 17-year-old.

Everything points to university as the default. It may cost you a lot in the long run, but that’s the long run, and today it’s so much easier than the alternatives. Our education system is designed for students who go straight from A levels to university. It is set up in a way that makes it easy for those who are good at exams. Their route is clear. It’s much tougher for the rest. The other routes are opaque.

This is mirrored in a public debate that focuses relentlessly on universities, their funding, their students, or the pay of their vice-chancellors, for goodness’ sake. That is not where the fundamental problems lie. It is our failure to get enough young people into high quality, job-based training at 18 that creates our skills shortages, low wages and productivity problems. If there is a problem with our universities it occurs when students fall into low value courses by default because that’s the easiest thing to do.

I have known this for years. You can see it in the data and the research — the evidence I spend my professional life sifting through. But it is not until it is part of your experience that you really feel it. Here’s an admission. Having done well by the exam system myself, if I’d stopped at one son I would always have had that little voice at the back of my head telling me that if I could do it, and if he could do it, then everything is fine. Maybe everyone else should just buckle down and get on with it.

I’d know intellectually that was nonsense, but I wouldn’t be able to help myself. That little bit of extra experience has changed the way I think. That, by the way, is why I believed David Cameron’s claim that the treatment received by his son Ivan brought home to him the value of the NHS in a way that mere theory never could.

If I were ever to become education secretary — God forbid — I would be a different one now. This self-knowledge has also shaped my view about the importance of having people with a diversity of experience at the top of politics.

Perhaps it shouldn’t matter if they have all been to public school and Oxbridge and are comfortably off. That doesn’t make them worse people. They are perfectly capable of understanding the evidence and sifting the options. But human nature is such that different experiences will lead them to understand that evidence, and weigh those options, differently. Perhaps this is most true of education policy where we are all too much influenced by our own, dimly remembered, schooldays.

Paul Johnson is director of the Institute for Fiscal Studies. This article was first published by The Times and is reproduced here with permission.