Scout and Jem are skeptical about joining Calpurnia at the Negro-only First Purchase AME Church. Scout knows that Cal's pride is at stake:
If Calpurnia had ever bathed me roughly before, it was nothing compared to her supervision of that Saturday night's routine...
"I don't want anyone sayin' I don't look after my children..." (Chapter 12)
The children of Atticus Finch were greeted warmly by nearly all of the congregation--all but the "troublemaker" Lula, that is. Lula does not appreciate Calpurnia bringing " 'white chillun to nigger church,' " and the reader is given a glimpse at what is probably the novel's only example of racial prejudice being displayed by an African American. Lula has " 'fancy and haughty ways' " not accepted by the more subservient Negro members of Maycomb, and Scout at first believes that Cal's other friends feel the same way.
... they did not want us here. I sensed... that we were being advanced upon. (Chapter 12)
But suddenly the threatening "Lula was gone," and the children were welcomed inside. Aside from some unusual practices, "Jem and I had heard the same sermon Sunday after Sunday" at their own church. It was a great learning experience for Scout, who "wanted to stay and explore." She also wanted to learn more about Cal, and Scout invited herself to spend a future day at Cal's own house. Scout's experience at the church led her to form her opinion that there really much difference between people--white of black. Unlike Jem, who believed that Maycomb had a special social tier,
"... I think there's just one kind of folks. Folks." (Chapter 23)