Upper middles classes like to perpetuate the myth that working class children aren't as ambitious as their children so they don't feel bad about the structural inequality they are complicit in.
This, absolutely.
Undoubtedly, there is a big factor in many cases of lack of support or aspiration and a limited world view - but this is by far the only reason. Plenty of rich people have very limited achievements, but because they have the family money to fall back on, they're glamorised and lauded as 'socialites' or 'debutantes' or 'personalities', even though they're only really famous for being famous.
There's a young man who pops up on TV a lot who is, as far as I can see, only famous because he's the heir to a very big biscuit company. He doesn't seem ever to have any particular skills or interest to offer other than being a celebrity. When it comes to aspirations, perseverance and a determination to make something worthwhile of his life, what's the real difference between him and somebody who works packing boxes in one of his family's biscuit factories - apart from one has millions at his disposal and the other is on NMW constantly struggling to keep their head above water?
Dismissing those from poorer backgrounds who don't end up making a big, lucrative career for themselves as being supposedly because they don't know that well-paying jobs exist is like suggesting that people must use foodbanks because they've never heard of supermarkets. You could go even further and say that starving children in desperately impoverished countries are only in that position because they're too dull to understand the benefits of eating regularly.
We all know that it's expensive to be poor, in so many ways. It's true that you can often 'speculate to accumulate' - but if you don't have the means to speculate in the first place, how can you ever get a foothold?
The last few governments have shown their clear desire to stamp on the faces of the ambitious poor and crush social mobility (well, upwards, anyway) with the introduction and continuation of university tuition fees. As a PP said, £30K+ of debt hanging over you is nothing to the wealthy (if they even bother to take out the loans in the first place), but it's an unfathomable rubicon to those from underprivileged backgrounds, however brilliantly academic they may be.
I know MN has a reputation for being solidly MC, but this has to be one of the most avowedly MC threads I've ever read on here.