In Harper Lee's To Kill a Mockingbird, why does Calpurnia scold Scout after making her leave the dinner table on the first day of school?
Calpurnia, who has been part of the Finch family since the death of Scout's mother, is not happy with Scout's observations of Walter Cunningham's table manners, and tells her so. Jem and Scout had invited Walter home for lunch on the first day of school after it became apparent he had nothing to eat; Scout, in her childish naivete and/or astonishment, comments loudly about Walter's dousing his lunch plate with molasses, to which Calpurnia responds by sending her to the kitchen, where she reminds Scout that Walter is a guest of the family, and is to be treated as such, unless Scout would like to finish the meal in the kitchen.
It is clear that Calpurnia is an important part of the Finch family. She does not hesitate to discipline Scout in front of Atticus, which speaks to the respect Atticus has for her contributions to the household. Aunt Alexandra, later in the book, suggests that Calpurnia is no longer needed to look after the children, but Atticus makes it clear that Calpurnia has been an important part of the family for too long and he has no intention of letting her go.
Calpurnia, who acts as a surrogate mother to the Finch children, scolds Scout for her rudeness toward Walter Cunningham while they eat their noonday meal.
In Chapter 3 Scout catches up to Walter, whom she blames for causing her to be punished by Miss Caroline (she tried to explain Walter's financial condition to her teacher so Walter wouldn't be forced to take money he couldn't pay back). During the lunch hour, she rubs Walter's nose in dirt in revenge until her brother Jem comes along. Hearing that Walter has no lunch, Jem invites Walter home to eat "dinner" with them after he recognizes that Walter is the son of Mr. Cunningham, who does some business with his father.
However, at the table when Walter pours syrup on his vegetables and meat, Scout is appalled. She asks "what in the sam hill he was doing." This embarrasses poor Walter, who replaces the syrup and quickly puts his hands in his lap. In disapproval, Atticus shakes his head. When Scout protests that Walter was ruining his meal, Calpurnia becomes furious, quickly requesting that Scout meet her in the kitchen. There, she tells Scout that some people do not eat as they do, but she has no right to criticize them.
"That boy's comp'ny and if he wants to eat up the table cloth you let him, you hear?"
"He ain't company, Cal, he's just a Cunningham--"
It is at this point that Scout is given a lesson in humility. Calpurnia sends Scout back to the table to retrieve her plate and bring it into the kitchen where she will finish her meal in shame.
Later, as Jem and Walter start their return to school, Scout lags behind in order to complain of her treatment and ask Atticus to send Calpurnia packing. Instead of agreeing, Atticus scolds Scout, reminding her of all the things that Calpurnia does for her. Further, he tells Scout to remind Calpurnia that she appreciates all that this woman does for her.