I know it's impossible to have a proper discussion of this in MN, but it is a huge problem.
And it's a problem the other way too.
My DDs went to 'naice' village school, mostly MC commuters and reasonably well off, very house proud, in work families.
We happen to live near to, about the only properly deprived, no stable job, boozing and generally dysfunctional family who has a child at the school.
She has an awful time, no one is actually nasty, but she gets left out and just sees everyone else with toys, clothes, cars, she can't dream off.
She comes round to play, only to find DD is at ballet, scouts, gymnastics.
She'd be hanging round like a lost sheep waiting for DD to get back.
Being poor and stuck in the back of beyond with no transport and almost no one your own age is no fun.
Being different from your peers weather richer or poorer or the only one of an ethnic group, religion or just the geek surrounded by 1D fans is always hard.
But I think money/class is hardest of all because it's so difficult to stop it permitting everything you are able to do.