Middle class students are less likely to work during uni, this makes the experience easier and generally better.
They also tend to have more money and greater support (especially upper-middle class. I assure you that many "rich" parents indeed give large allowances).
Their parents have gone to uni and they have always been expected to do the same, so it feels natural for them (less stress, more confidence). Their family might have gone to the same university/college which means you feel as if you own the place more, and also have useful contacts (among the upper-middle class I see that parents can give their children privileged access to support and guidance from faculty and administrators).
It's more likely that your school has prepared you at best for university if you are middle class or above.
Working class people are excluded from certain social circles in uni, where people have lavish parties, dine in nice places and go on expensive trips.