In Chapter 3 of "To Kill a Mockingbird," does Scout learn anything from Walter's visit, and if so, what?

Scout learns many things from Walter's visit.  Social codes and caste systems are key issues throughout the novel.  This is Scout's first introduction to both of those ideas.  First, thanks to Calpurnia's reprimand for shaming Walter when he pours syrup all over his lunch, Scout realizes that there are social guidelines one must follow when company is over.  Cal tells Scout: "'That boy's you' comp'ny and if he wants to eat up the table cloth you let him, you hear'" (24)?  Cal is trying to impress upons Scout the idea of Southern hospitality. 

Scout defends herself by declaring that Walter isn't proper company, he is just a Cunningham, who are one of the poorer families in Maycomb.  In this way, Scout has bought into the idea that certain people are superior to others because of their names, histories, and wealth.  In terms of a caste system, the Finchs would be near the top and the Cunninghams would be farther down.  This is the opposite of what Atticus wants Scout to think.  Note too how Atticus treats Walter at lunch, talking about farming with him and treating him properly.

This chapter foreshadows several key events to follow in the novel, such as Scout's ability to diffuse the angry mob that comes to lynch Tom Robinson (see the second link below) and Aunt Alexandra's refusal later in the novel to allow Scout to be friends with Walter because he is white trash (see the final link below).