I get irritated by sweeping generalisations that do not stand up to scrutiny and amount, sometimes. to socially approved cliches. rather than careful study.
I doubt anyone rich or poor goes through life without for, sometime longish periods, feeling isolated lonely, different or out on a limb, especially when they are children. It is a normal part of life.
Many of those with expensive goods are the children of parents who find it easier to spend money on their children rather than give them time and attention. This is especially so when parents are separated or divorced. A poor child from a loving home is far better off than one caught in a game of pingpong between separated parents who have no time for their child so just shop for them.
In any class there will be as many children from poor homes as rich, Vintage may be a fad, but it is a cheap fad, especially if you can sew and turn old clothes into new.
It is this parcelling into children into huge groups rich and with designer goods, poor and coming barefoot to school (yes I know that is an exageration), but no more than defined before.came before. Any big school will have children in all sorts of groups affinity, activity, sporting, hobby, and every child will belong to several. these simplistic cliched groups deny every child the right to not be in those groups.