Why does lee include the information on mr. cunningham's dealings with atticus in the middle of classroom scene?

Harper Lee included the information about the Cunninghams in the classroom scene to provide a form of introduction to the family to the readers.

Explanation:

Harper Lee's "To Kill A Mockingbird" tells the story of the town of Maycomb in the American south, where there are still traces of racist prejudices. The story also deals with the themes of isolation, prejudice, good and evil but most importantly the importance of moral education despite the majority opinion.

In Chapter 2 of the text, we are introduced to the classroom scene of the town where Miss Caroline tried to lend lunch money to Walter Cunningham. And in a bid to familiarize the teacher with the Cunninghams and their ways of living, the author through Jean "Scout" Finch, gave a look into the family. And with this act of making Scout talk about the Cunninghams to the teacher, we, the readers are also introduced to them indirectly.

Not only that, the author also included the conversation that Atticus Finch had with his family amidst the school scene. The two references about the Cunninghams, even though Scout admitted she "could (not) have explained the things to Miss Caroline (that Atticus had told his children), I would have saved myself  some inconvenience and Miss Caroline subsequent mortification, but it was beyond my  ability to explain things as well as Atticus", gave a pretty good information about the Cunninghams for the readers to know.

the african society basically suffered the consequences of colonization and apartheid directly attacking the black people, first, during the colonialism and its main idea which which "white people" had better rights, affecting   them principally in the right to establish black people in their territories, access to quality education and health services and took away any civil right even to the black people to feel they have the same opportunities as the settlers.