In chapter 12 of Harper Lee's novel To Kill a Mockingbird, Calpurnia demonstrates her affinity to the Finch family by bringing the Finch children, Scout and Jem, to her church on Sunday.
The the fact that Calpurnia is taking the children there shows how she is beyond racial separation or differences when it comes to the Finch kids. She loves them and cherishes them as if they were hers.
However, three main incidents occur during that visit. All three provide insights into the black culture of Maycomb, into Calpurnia's life, and into Scout's own identity.
First, the Finch kids notice almost immediately that they are not welcome by the rest of the congregation even though their father was the person defending Tom Robinson.
In Scout's own words:
I sensed, rather than saw, that we were being advanced upon.
A church member, Lula, confronts Calpurnia asking her how come she is bringing white children to a black church. Calpurnia defended her decision and moved on.
It's the same God, ain't it?
Two things are important here. Scout realizes that Calpurnia speaks differently than the way she speaks at the Finch household. She even asks Calwhy she is talking their slang. This is yet another lesson for Scout, for Calpurnia says:
You're not gonna change any of them by talkin' right, they've got to want to learn themselves, and when they don't want to learn there's nothing you can do but keep your mouth shut or talk their language.
Another interesting observation is that First Purchase church is also what gives all the black citizens of Maycomb a sense of uniqueness, unity, and belonging. Bringing a white person to First Purchase, regardless of who that white person is, would be like bringing a stranger to a family gathering. To top it, this stranger belongs to the race which oppresses them the most. It may have been too much for them to accept.
Second, Scout realizes the level of chauvinism in the words of the sermon “Impurity of Women Doctrine". In it, women are referred to as the worst and most problematic part of society. The putting down of women in the sermon is, undoubtedly, a technique to instill shame and guilt in women so that they can become even more subservient. However, Scout is a growing feminist and she clearly seems bothered by the comments the pastor says. Yet, she receives an advice for Jem, who tells her to take note and start behaving like a lady. This is one of the few times when we see Scout almost taking Jem's advice seriously. Of course, she does not change right away, but surely this experience will somehow affect her future.
Third, Scout gets yet another lesson in community when she sees that all church goers collect money for Helen Robinson, Tom's wife, who (due to the case) cannot find employment. They are all determined to make ten dollars for her. This is another side of Maycomb that Scout has never seen.
Finally, it is because of the experience in church that the Finch kids get their invitation to go to court and sit where the black people were forced to sit so that the kids could watch the trial. The reverendwas kind enough to accept them and invite them. All this was a huge growing experience for Scout and Jem, who were already seeing the changes in their own lives as they were slowly growing more mature.