My children went to a school in a very mixed area, and I always tried to invite as many children as I could to parties irrespective of their background. Still in primary school, DD was invited to the party of one of her friends who came from a very poor family and I must admit I took her (snob alert) with some anxiety just not knowing what to expect. The mother welcomed her in and I caught a glimpse of the party table. Doorstep sandwiches with huge slabs of cheese, all the crisps, pop, E numbers you could think of and certainly no little niceties in terms of party food or decorations. My daughter (around 6 at the time) came home saying it was 'the best party I've ever been to'. I think it was because she felt welcomed, had fun, and the adults genuinely liked children and no one stood on ceremony. A lesson to me to look at people through a child's eyes!
Sorry, I digress, but I think Grannyknot's mum had it right and the lesson to be kind (and non-judgmental) is the most important one we can give our children.