I was brought up on a rough council estate and studied and worked hard to improve my life and provide a good upbringing for my children. The difference being that despite illness and having 7 kids, my parents pretty much always worked, at sometimes both of them, which was not that usual in the 70s, my Dad did nights and watched us days, my Mum worked days and sorted out the house at nights - all our clothes were hand made as were our meals. It is the example that we were set that has made myself and my brothers and sisters who we are today.
My kids have what I would class as a midle class upbringing but go to the local school with the kids from the local council estate and whilst I make them speak properly in our house and in our company, I would not have them putting down any of the kids on the basis that they are from a disadvantaged background.
How the parents of that posh girl, apparently intelligent people, allowed her to carry on believing those stereotypes beggars belief.