In To Kill a Mockingbird, explain the kids' experience when they attend church with Calpurnia.

In general, I think the best way to answer this is to say
that the two kids have a "how the other half lives" experience when they go to the First
Purchase Church with Calpurnia.  While they are there, they actually see black people
living in a "black world."  They see (as much as possible) how black people act when
they are away from whites.

For example, they learn about
the differences in resources available to the races.  They see this in how poor the AME
church is -- no hymn books, for example.  This also brings home how illiterate most
blacks are.

Another example is that they see Calpurnia
talking like the other blacks do (she doesn't talk that way to them).  This starts to
teach them about how more educated blacks need to act in the black
community.

In general, then, they start to learn more about
the details of black life -- this is something they would not have cared about and not
usually had the opportunity to see.