In Chapter 3, Walter Cunningham Jr. eats dinner with the Finch family and pours syrup all over his meal. Scout is astonished and disgusted at Walter Cunningham and rudely comments on his dinner manners at the table. Atticus immediately shakes his head at Scout in an attempt to make her stop commenting on Walter's manners before Calpurnia takes her into the kitchen to teach her a lesson. When Scout gets into the kitchen, Calpurnia chastises Scout for her rude behavior. Calpurnia tells Scout that she should respect her guests regardless of their background and tells her to never disgrace anyone at the dinner table again. The readers learn that both Atticus and Cal are polite individuals with high moral standards. Both characters also understand how to treat their guests with respect. Atticus and Cal believe in correcting Scout's behavior which also displays their interest in raising well-behaved children.
This is a good question. We learn a few important things about Atticus and Calpurnia when Scout criticizes Walter's eating habits. First, let me give the quote:
Atticus shook his head at me again. “But he’s gone and drowned his dinner in syrup,” I protested. “He’s poured it all over-"
It was then that Calpurnia requested my presence in the kitchen.
She was furious, and when she was furious Calpurnia’s grammar became erratic. When in tranquility, her grammar was as good as anybody’s in Maycomb. Atticus said Calpurnia had more education than most colored folks.
First, we see that both Atticus and Calpurnia were disappointed and angry at Scout for what she did. This shows that they did not approve of Scout's behavior.
Second, as we probe into the reasons of why Atticus and Calpurnia were angry, we learn that they valued hospitality. When someone comes to share a meal, they can do whatever they want. And it is rude to impose personal habits, as Scout has done.
Third, Atticus and Calpurnia are people who try to see things from the perspective of others. Therefore, when Scout only saw things from her own eyes, they were not pleased with her lack of sensitivity.
In short, we learn that Atticus and Calpurnia are good people. Scout is still learning.