Very controversially, I think the end result of decades of social security policy has come home to roost, along with a decimation of our manufacturing industries and reliance on posh young men in red braces to run our economy.
We have, still, one of the highest teenage pregnancy rates in the developed world. It stands to reason that, among the many young people who get accidentally pregnant and use the event as a trigger to pull their socks up, decide to get a decent education so as to be able to provide for themselves and their baby, thus maybe even achieve a better life-outcome than they otherwise may have done; there are a fair slab more who shrug, 'safe' in the knowledge it doesn't matter, thus leave school with nothing, certainly no education - whose DC stand little chance of getting the support they'll need to succeed at school themselves. With the best will in the world, it's quite hard to pick up and run with your DC's Y8 or 9 chemistry homework to assist them if you're out of your depth with Y4 English, a situation that just might also involve your poverty, your sub-optimal housing, a limited support network, no culture of self-reliance or self-improvement (see remarks made by others that our OECD standing might be better if our teachers spent more time teaching and less social-working!).
I also think it would be hard to model desirable behaviours such as regular work-going, self-study (and the self-discipline to do it) to gain advancement at work and so forth, plus demonstration of the visible signs of 'success' such as a nice enough home, a reliable car, even foreign holidays if you can bring none of that to your 'domestic table'.
This is absolutely not a 'bash the poor' tirade, it's meant to be a further exploration as to why the UK does relatively so badly against other countries with different policies towards benefits, views regarding single parenthood, social responsibility, cycles of entrenched poverty. (Though again, I think if you were to take the DC who were tested from certain areas of the country, the results would be very different from if you took the DC from, often, the neighbouring borough).
We are quite a divided nation and, to me, it seems we want to keep it that way if we're on the winning side. We absolutely would refuse to pay the sorts of taxes the 'more successful' Scandinavian countries do; we don't have a cohesive social 'pact' with each other, we don't have industries that can employ (thus empower) our academically less able like Germany does.