Scout states that there is a "caste system" in Maycomb. how does she explain the system?

A caste system the device people along lines such as Financial or racial. and may come there is the upper class represented by the rich white people such as Atticus and his family. There are the poor black citizens like Tom Robinson.

Other white middle-class citizens are represented like the jury.

And then there is the "poor white trash" represented buy Robinson's accuser.