Because Walter Cunningham has no lunch to bring on the first day of school, Jem acts as peacemaker between Scout and Walter after Scout rubs his nose in the dirt in the schoolyard. For, after learning from Scout that Walter has caused the teacher problems by not having any lunch, Jem invites the boy to their home to eat with them in reparation for Scout's cruelty.
At the table, the hungry little Walter piles food upon his plate; then, he asks for molasses. When Calpurnia returns with the syrup pitcher, she watches as does Scout while Walter pours syrup over his vegetables and meat; appalled, Scout asks him "what in the sam hill" he is doing. Furious at this rude remark to the embarrassed Walter, Calpurnia takes Scout into the kitchen. There, reverting to dialect in her anger, Calpurnia scolds Scout, whispering "fiercely,"
"There's some folks who don't eat like us...but you ain't called on to contradict 'em at the table when they don't. That boy's yo' comp'ny and if he wants to eat up the table cloth you let him, you hear?"
Continuing, Calpurnia chides her about politeness to any guest in their home, telling her that if she cannot act properly at the table, she will be relegated to the kitchen.
In this scene from Chapter 3, Calpurnia clearly demonstrates her role as surrogate mother for the children, a role of which Atticus obviously approves. No ordinary maid, Calpurnia is an integral part of the Finch family, treated as though she is truly a relative.