What matters is the ambition and how hard children want to work to succeed.They grew up as working class children by most definitions they are now middle class.This class divide is not static and can be bridged by those who want to overcome those hurdles.
However, I do believe that the environment can make things easier
Depending on personality, family environment, you may be strong enough to fend off. Or you may fail.
Not sure if there are studies on the topic, but all my anecdotal evidence (based on myself, friends, family), show that you have a higher chance of being an achiever if you are surrounded by achiever, and a higher chance to give-up if you are surrounded by people who give-up.
And since "people" is not made exclusively of family, but also includes friends, other pupils, teachers, the broader world, TV, etc... it could be a disadvantage to go to school where the only ambition kids have is to survive rather than aim for the stars.
I agree. Its much easier to achieve your potential if your friends, family, school, parents etc all expect you to and have all done so themselves. Its much harder if you are surrounded by people who couldn't care less if you work or not or friends that try to get you involved in bad ways or whatever.
Totally and utterly surmountable of course, given determination. I know many who have and I admire them, especially those who came from totally uninspiring backgrounds. But it I'm honest? I'm sure my ambition and drive was as much due to the 'expectations' around me as my own inner drive and I'm grateful for that. And that is why I am a fan of selective and private education, although not seeing it as either guarantee or fair on those who can't access the system.
Utopia of course, as has been said before, would be to have totally state funded and excellent schooling - with a mix of clever/less academic rich/poor motivated/non-motivated in each one, but of course that can never happen as those who can afford it will always congregate around a perceived 'best school' - thus driving up the property prices and driving out those who would benefit most from the great school. Hard to know what to do, which doesn't mean we shouldn't constantly assess and see how far towards it we can go.