One of the most important things that the children learn from their visit to Calpurnia's church is that, despite differences in worship methodology, church was essentially the same as going to "white church."
Through their encounter with an unfriendly woman at the outset of the service, they also learn that difference is guarded against in other social circles, as well.
However, due to Calpurnia's calming influence and her defense of the children, they also figure out the true value of Calpurnia as a friend as well as a household member.
In chapter 12 of "To Kill A Mockingbird," Calpurnia takes the kids to church. Miss Lula storms up to her and wants to know, "why she bringin' white chillun' to a black church." "The children find that they are not warmly accepted by all members of the First Purchase African M.E. Zion Church. The children find similarities—and differences—between the church they normally attend and the church to which Calpurnia takes them. They also learn that hatred goes both ways. On the way home, the children get to know Calpurnia better. They begin to regard her as a fine friend and as a real person with a life separate from her life with them."