There are always exceptions.

But may I ask when your kids were being invited places? I know that the more things change, the more they stay the same, but I'm guessing there was a lot more movement/interactions among classes even twenty years ago.

Also there's some socializing...but then there's getting tutoring and lessons from the top-priced experts, the sorting into the best and most expensive schools and colleges, the assortative marriages to each other--and pretty soon it's just more rare that people doing anything substantive together across class lines.