They aren't cory, but unfortunately the type of parent that I saw at the bad school DD went to was all too often one who fell into the 'had children too young, didnt have a clue what to do with them, and sat at home on benefits all day' therefore couldn't afford to live in an 'affluent' area, plus many of the children I know that do live in an 'affluent area' have parents who worked hard to afford where they are and appreciate education because for it, therefore may have problems with their childrens behaviour but not as often WRT school .
I think the respect a person gives to a teacher also makes a huge difference, and many of the parents at the 'bad school' were of the mentality that their child was being picked on by the teacher, and that the teachers were jumped up snobs, because they had been boguht up the same way by their own parents, and perpetuated the cycle, not realising that attitude was partly to blame for why they had not become finacially successful in life.
I just want to point out however, that I too had children young, had no education behind me, have lived in council properties, been a single parent on benefits etc, I am not saying all, or even the majority of parents in those circumstances are like those mentioned above, but more the reverse, parents like the above are less likely to achieve because of their frame of mind.