How does class stratification perpetuate systemic inequality?

Basically, like soil, the society is divided into classes, most commonly based on wealth, so you have the upper class, the middle class, the working class, and the lower class which is basically a nice term for poor people. Because of such stratification, those belonging to certain classes have limited access to other classes and it's difficult for a lower class person to become a middle class or an upper class person. This more or less means that there is a high chance that you will remain in the class that you were born in. This causes a lot of inequality on a state wide basis among all people.