There is lots of evidence that states that below a certain income or the environment your children are brought up in affects their self-esteem. Take council estates - how many children grow up happy and successful? I'm not talking about people whose income is too low to afford private school, but those children who are clearly deprived. If you are deprived then how can your self-esteem be high, every day is a struggle.
And I'm talking from personal experience - there were days where my mother went without food to feed us. Even if I'd gone to one of these top schools I would have felt even worse about myself when I saw the wealth that these kids had. I was clearly one of the brightest in my year at school but I ended up dropping out and truanting and it was the kids who had a more secure family life that did better in school and in life. So if you think I'm generalising about the self esteem of deprived children, then maybe you should ask yourself if you've ever experienced extreme deprivation or been around it long enough to see it's impact. Being PC doesn't get us anywhere, the facts are the facts. A family needs to be lifted out of deprivation, not one child from that family.