Alexandra is a strong believer in Southern tradition; one of the traditions of the Old South she continues to uphold with great zeal is that of social class distinction. Put simply, Alexandra is a snob. She is enormously proud of her family heritage as a member of the Finch family, one of the oldest and most respected in Maycomb County. As a result, she looks down upon any family that is not as old and accomplished (or as financially comfortable) as her own. It is from this frame of reference that Alexandra explains to Scout why she cannot be friends with Walter Cunningham, a classmate who comes from a poor but proud family:
The thing is, you can scrub Walter Cunningham till he shines, you can put him in shoes and a new suit, but he'll never be like Jem. Besides, there's a drinking streak in that family a mile wide. Finch women aren't interested in that sort of people.
When Scout persists, Alexandra speaks as plainly as she can, showing her ignorance and arrogance about Walter, a respectful little boy who cannot help the circumstances of his birth:
Because--he--is--trash, that's why you can't play with him. I'll not have you around him, picking up his habits and learning Lord-knows-what.
Her Aunt's contempt and cruelty reduce Scout to furious tears. Jem leads her sobbing from the room.
In Chapter 23, Atticus explains to the children that one of the Cunninghams argued for Tom Robinson's acquittal. This news shocks the children and Scout suddenly remembers the time that she rushed to Walter's defense in school. When Scout mentions that she is going to invite Walter over to play and spend the night, Aunt Alexandra says, "We'll see about that" (Lee 137). Scout is perplexed, and Aunt Alexandra proceeds to explain why Walter Cunningham Jr. cannot come over. Alexandra believes that the Finches are a more esteemed family than the Cunninghams and she is prejudiced towards them because they are lower-class farmers. Alexandra ends up telling Scout that Walter Cunningham Jr. is "trash" which infuriates her. Aunt Alexandra believes that upper-class families should not mingle with lower-class families and fears that Scout will pick up on Walter's bad habits. She views the Cunningham family as beneath them and forbids Scout from playing with Walter despite the fact that he is a well-behaved child.