The key difference must be knowledge of how society works in order to live a life that you can choose.
As I said, I did well at state primary. Of my five closest friends, all were from working families. Parental occupations were teacher, teacher, factory manager, teacher, factory fitter, Secretary, process operative, small scale catering business owner (think funerals and wedding anniversaries), photography shop owner, SAHM, teacher, scientist. Three of us played an orchestral instrument. One rode. None of us played any serious sport. 5 of us did Duke of Edinburgh. 4 went to guides. 2 edited the school yearbook. One family used to drive around France on holiday which we all thought was a bit odd. Our parents didn’t really know each other at all. We used to go to the cinema, the local youth club, and then gigs when we were older.
We all did alright academically.
BUT…. We had no clue about ‘reading round your subject’, we were just passing exams! Two of us wanted to do medicine and law, no one from our school sixth form had ever done that. Only one person from our school had ever been to oxbridge. Our school work experience was dominated by working in local schools, factories, offices and shops… there was very little planning to it. I’d nearly finished university before I was able to put together what gap years, internships and training contracts were, by which time it was too late.
That’s the difference. Its knowing that that this stuff exists, that people live different lives to you, and that the opportunities are even there…. Let alone taking advantage of them.