Lula believes white children do not belong in a black church.
Lula is not happy to see Scout and Jem with Calpurnia at First Purchase because it is an African-American church and she doesn’t think white children should be there. When Calpurnia tries to tell Lula that Scout and Jem are her company, Lula objects, saying Calpurnia is not company at the Finch house during the week.
Lula stopped, but she said, “You ain’t got no business bringin‘ white chillun here—they got their church, we got our’n. It is our church, ain’t it, Miss Cal?”
Calpurnia said, “It’s the same God, ain’t it?” (Chapter 12)
Scout and Jem become uncomfortable during this altercation and want to go home. Calpurnia refuses to be intimidated. Scout is surprised to hear her speaking like the other African Americans because she is used to hearing her use the language and grammar the town's white people use. She doesn’t realize most African Americans do not have access to education, so speaking like a white person would make Calpurnia an outsider when she is at church.
Calpurnia’s son Zeebo gives Scout and Jem a warm welcome and tells them not to pay any attention to Lula.
One of them stepped from the crowd. It was Zeebo, the garbage collector. “Mister Jem,” he said, “we’re mighty glad to have you all here. Don’t pay no ‘tention to Lula, she’s contentious because Reverend Sykes threatened to church her. She’s a troublemaker from way back, got fancy ideas an’ haughty ways—we’re mighty glad to have you all” (Chapter 12).
Although Zeebo welcomes the children, he is also extra polite and respectful. He treats Jem and Scout this way because they are white. Although Jem is younger than Zeebo, Zeebo calls him "Mister Jem." He is essentially proving Lula's point, even if he doesn't mean anything by it.