The idea of inequality means different thing to different people. However, we all use the word. To relate it to society, Karl Marx comes to mind. Every state with capitalist view is always full of classes. In school, we have captains, prefects, HOC, etc. These people are mostly chosen based on their academic perfomances which suggest class ultimately.

Except we can have a communism as proposed by Marx, class struggle and dominance will continue.

Thanks.