In Harper Lee's To Kill a Mockingbird, Walter Cunningham comes home with Scout and Jem at lunch on the first day of school. Scout had tried to explain Walter's reason for refusing to borrow a quarter from Miss Caroline for lunch, and was eventually punished because the teacher did not understand the situation or what Scout was trying to say. As they leave school, Scout jumps on Walter, blaming him for her difficulties in the classroom. Jem stops his sister and invites Walter home for lunch.
First, as Atticus and Walter speak, the boy describes why he has never passed the first grade—
"Reason I can't pass the first grade, Mr. Finch, is I've had to stay out ever' spring an' help Papa with the choppin', but there's another'n at the house now that's field size."
"Did you pay a bushel of potatoes for him?" I asked, but Atticus shook his head at me.
Scout understands that poorer folks (e.g., farmers) sometimes must pay for services with goods, as Walter's father paid Atticus for legal services. Atticus has also mentioned that other people are paid the same way, including doctors—hence, Scout's question as to whether or not the family had to pay the doctor for the baby's delivery with a bushel of potatoes. This child, Walter notes, is now "field size," or rather, able to work in the fields.
The next thing that Scout has to say is about Walter's use of syrup on all of his food:
He would probably have poured [syrup] into his milk glass had I not asked what the sam hill he was doing. [...]
"But he's gone and drowned his diner in syrup," I protested. "He's poured it all over—"
Calpurnia calls Scout away from the table to speak to her privately in the kitchen about her manners.
This scene demonstrates the difference between the economic status of the Finch family and others in the community. While the Finches are able to afford a nice house and Calpurnia's help with the cooking and raising the kids, Atticus has told them that they are poor.
In this instance, Calpurnia wastes no time telling Scout that the Finches are no better than their neighbors. While Scout understands the concept that there are differences between her and others (and has difficulty keeping her opinions to herself), she is not a snob. Her father explains the economic and social disparities around them and Scout generally takes people for who they are—not based upon their wealth or social standing, but based upon how they act, especially with her and her family.
While Aunt Alexandra sees these gaps, Atticus makes certain that his children are down to earth, being kind to, and tolerant of, others.