The Finch children go to Calpurnia's church.
At the beginning of the chapter, Scout is worried about her brother Jem because he is acting strangely. They seem to have grown apart. He eats a lot, and seems to act more like an adult. Scout finds this disturbing.
Scout is even more depressed when Dill does not come as he normally does for the summer. Instead he sends a picture of himself with his new father. The state legislature is called into emergency session, and Atticus has to leave for two weeks. Scout is all alone.
Since Atticus is away, Calpurnia takes Scout and Jem to church with her. She does not trust them to go to church alone, because there was an incident with some kids at church unsupervised before. Cal makes sure the kids are cleaned up well, and fusses over their clothes. She wants to make a good impression.
When they arrive, they are greeted by Lula, a woman at Calpurnia’s First Purchase church (called so because they bought it themselves), who accosts Cal and the children. She is not happy that Cal brought white children to her church. While most people are respectful and polite to the Finches, Lula is plain rude. Cal defends them.
"They's my comp'ny," said Calpurnia. Again I thought her voice strange: she was talking like the rest of them.
"Yeah, an' I reckon you's comp'ny at the Finch house durin' the week." (Ch. 12)
Although Lula says that the whites have their church and the blacks have theirs, Cal comments that it is the same God.
Scout is surprised at Cal’s simple speech when she talks to Lula. Although Cal is educated, she codeswitches when she is among the people at church. In order to fit in and not seem pretentious, she talks the same way they do.
Scout is also surprised that no one at the church other than Cal and her son Zeebo can read. Cal got her education from the Finches, but it is rare among her population. The black church sings hymns through a method called “linin’” where the person who knows how to read reads the line and the others repeat it.
At the church, Reverend Sykes collects money for Helen Robinson, reminding everyone that with Tom Robinson’s legal troubles the family needs help. This puts the Robinson case in broader perspective, and reminds the reader that he has a family too. Cal will not allow the Finch children to contribute.
On the porch when the children return they find Aunt Alexandra.
I looked down the street. Enarmored, upright, uncompromising, Aunt Alexandra was sitting in a rocking chair exactly as if she had sat there every day of her life. (Ch. 12)
This is significant, because it demonstrates that a change is about to occur in Scout and Jem’s home life. Atticus did not want to go off and leave his children alone for long, and with the trial coming Alexandra wanted to be there to be an influence for them.