I don't believe that these "two groups" could not be friends and frequently socialise.
Everyone can be, but most of us don't - that's what class is about, isn't it.
look who was a vice prime minister in Poland:
I can assure you it wasn't him.
Note also that in Poland besides Warsaw there are no better or worse districts
This is simply not true.
In one apartment can live a layer, a doctor and a coal miner.
They each have rather different purchasing power!
My school friend was attending to one school with daughter of prime minister - Marysia Belka
Her parents are both charming people - very friendly, and don't take the trappings of prestige for granted.