Atticus refers to the common folk as people of society who follow the laws and go to school, have jobs, and attend church. When talking to Scout, he says that the Ewells are not common folk, they are special. They do not live in society, they live on the outside of it. He explains that they only go to school one day a year because the rules are bent for them (they are breaking the laws but are not hurting other people so they are left alone).