In Harper Lee's To Kill a Mockingbird, by using inferences, I believe we can accurately assume that although Lee does not write the words that the children were welcome at First Purchase Church, irrespective of who they were, the actions of most of the black congregations shows that they were.
Although Lula approaches Calpurnia with anger over the presence of Jem and Scout, white children, in a black church, the rest of the congregation does not agree with Lula's attitude or behavior. While Scout and Jem are worried about their reception, the congregation does a great deal to allay their fears.
After Lula confronts Calpurnia, Jem suggests that they leave.
Jem said, "Let's go home, Cal, they don't want us here—"
I agreed: they did not want us here. I sensed, rather than saw, that we were being advanced upon. They seemed to be drawing closer to us, but when I looked up at Calpurnia there was amusement in her eyes. When I looked down the pathway again, Lula was gone. In her place was a solid mass of colored people.
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…we're mighty glad to have you all."
With that, Calpurnia led us to the church door where we were greeted by Reverend Sykes, who led us to the front pew.
Though Lula confronts Calpurnia about the presence of white children in the black church, Lula is not representative of the feelings of the rest of the congregation. True to what Calpurnia alludes to in her "argument" with Lula, "It's the same God, ain't it?"
At the First Purchase Church, the children are treated with Christian charity and good will. These people live what they are taught in church, and we could assume that they are better Christians than most of the people in Maycomb who we later learn will not allow Christian love to find Tom Robinson "not guilty" because they cannot see past their prejudicial hatred to do so.