The juxtaposition of Aunt Alexandra's arrival with the children's attendance at Calpurnia's church points to several sharp contrasts, contrasts that make Jem and Scout aware of the hierarchy of social positions--"the caste system"--in Maycomb as well as the hypocrisy. While Jem and Scout's visit to Calpurnia's church has revealed to them an entirely different side of life from theirs, Calpurnia has thus led the children more into a real world. But, Aunt Alexandra's talk of family history and "fine folk" is remote and artificial.
When she arrives, Aunt Alexandra informs Scout that she is there to provide "some feminine influence." However, unlike the charitable Calpurnia who invites the children to her church, holding her tongue when Lula insults her, Aunt Alexandra, Mrs. Merriweather, and the ladies of the Missionary Society are later not reticent about their biases:
"I tell you there are some good but misguided people in this town....Folks in this town who think they're doing right, I mean....but all they did was stir 'em up."
Nor is Aunt Alexandra. For, shortly after her arrival, Alexandra displays her lack of charity and disapproval of Scout's being raised by Calpurnia, by asking Atticus to dismiss her. However, Atticus defends Calpurnia as a valued member of their family, thereby reinforcing Calpurnia's lessons and putting Aunt Alexandra's idea in opposition to them. So, after having been exposed to Calpurnia's example and her world, Scout and Jem detect the hypocrisy in Aunt Alexandra's "caste system" and her allusions to what is proper.