In chapter 3, young Walter Cunningham has been invited to a meal after Jem found his younger sister beating him up over a conflict with their teacher. Scout is already in a foul mood, exasperated with Miss Caroline for not understanding the ways of Maycomb more quickly.
When Walter sits down for the meal, he requests molasses. Because his father doesn't have the financial resources that the Finch family possess, molasses is likely a treat that isn't readily available at the Cunningham residence. Thus, Walter pours it over everything, even his vegetables, which horrifies Scout. She asks him what the "sam hill" he's doing, and Calpurnia pulls her into the kitchen.
Calpurnia, who often stands in as a maternal figure for the Finch children, reminds Scout that Walter is her guest. This likely irks Scout for two reasons. First, she hadn't invited Walter there in the first place. She was rubbing his nose in the dirt when her brother had intervened and invited Walter to their home. Scout's rebuttal to Calpurnia's classification as their "guest" provides further insight into her character at this early point in the novel. She retorts that Walter is "just a Cunningham."
As a lawyer's daughter, Scout is afforded a better lifestyle than some other people in town. Because of her last name and family ties to Maycomb, she is treated with more respect than some other families. She is just a young child, but she has already begun to absorb the class structure in Maycomb, as revealed by this comment. Whether listening to the way Miss Caroline treats students with "cooties" or learning social etiquette from Aunt Alexandra, Scout has already developed a perspective about the advantages of being a Finch—and the disadvantages of being a Cunningham.
Calpurnia quickly admonishes Scout for her skewed perception as it does not reflect the views of Atticus. She tells Scout, "Anybody sets foot in
this house's yo' comp'ny, and don't you let me catch you remarkin' on their ways like you was so high and mighty!" Because Atticus leads through example and invests a great deal of time into meaningful conversations with his children, never shying away from difficult topics, Scout learns to value people because of their character, not their financial status.