Simplify the following text for a Grade 5 native English-speaking person.
Original: For example , a simple stratum model of class might divide society into a simple hierarchy of lower class , middle class and upper class , with working class not specifically designated . Due to the political interest in the working class , there has been debate over the nature of the working class since the early 19th century .
Simplified: Working class contrasts with middle class and upper class .