lower class 
noun [treated as singular or plural]
The social group that has the lowest status; the working class: in popular fiction of the past, villains were usually of the lower class the highest mortality was found in the lower classes...
- The society is made up of the wealthy upper class, the middle class, and the working or lower class.
- But all the projects are aimed at either the upper class, the middle class or lower class, there is nothing for the absolute poor.
- I'm so sorry for the gap between the middle class and the lower class.
adjective
Relating to or characteristic of the lower class: a lower-class area...
- It is also true that high-risk characteristics are common in lower-class communities.
- Granted, it is a lower-class area, but the majority of the people living there make no effort to improve their lives.
- In urban areas, lower-class men work in crafts, manufacturing, and low-paid service industries.