When Walter first arrives, Scout is amazed at how Atticus treats Walter like an equal. He discusses farming with Walter as if they were two old farmers. Unlike other members of Maycomb, Atticus does not conform to or dwell on class distinctions of the town. Atticus always tries to understand things from the perspective of others. That's why he talks about farming with Walter; he knows this is something Walter has had experience with.
When Walter drowns his food in syrup, Scout criticizes him for it. Calpurnia scolds Scout and Scout replies by saying "he's just a Cunningham." Calpurnia teaches Scout that wealth and education do not make a person better than one who is poorer or less educated.
Yo‘ folks might be better’n the Cunninghams but it don’t count for nothin’ the way you’re disgracin‘ ’em—if you can’t act fit to eat at the table you can just set here and eat in the kitchen!
This lesson, of judging people based on their character rather than on their wealth or education, does not really sink in for Scout in this chapter. When Calpurnia is nice to her, Scout thinks that Cal had seen the error of her ways - referring to when she scolded Scout for criticizing Walter. The larger lesson of considering another person's perspective and place in life is something Scout will continue to learn throughout the novel.
Absolutely. Before Walter is invited to the Finch home for lunch, Scout is scolded by Jem for beating up the boy who was much smaller than she. She discovers that young Walter and Atticus have something in common: They "talked together like two men... expounding upon farm problems" before Walter decided to "drown" his entire meal in molasses. Scout quickly learns that she should control her tongue after she insulted Walter for his uncontrollable sweet tooth. Calpurnia escorted Scout into the kitchen where she chewed her out in a "furious" fashion. Scout learned that
"... anybody sets foot in this house's yo' comp'ny..." (Chapter 3)
Scout also learned from Cal not to be " 'so high and mighty!,' " and that even if the Finches were " 'better'n the Cunninghams,' " Scout's actions were a disgrace to any house guest. Later, Scout has second thoughts about Walter, and she recognizes that he is nothing like some of her other poor classmates such as Burris Ewell. Scout also learns that Cal can be forgiving when she returns home to find that the housekeeper has prepared one of her favorite foods--crackling bread--as a peace offering.