What insights do Jem and Scout gain from attending church with Calpurnia and why is it special to Calpurnia in To Kill a Mockingbird?

Above all else, Jem and Scout gain valuable insight to the
very different lives of Maycomb's African-American population. Calpurnia is obviously
very proud of the Finch children and makes sure that they are looking their best when
they arrive at First Purchase A.M.E. She is also very proud of her church, and though it
is not mentioned much in the novel, Calpurnia is a spiritual person whose church life
plays a major part of her life. Calpurnia takes the children specifically because
Atticus is out of town, and she does not trust the kids to attend their own church
unsupervised.

Among the things that the children learn
during their visit:

• The definition of "linin',"
  in which the mostly illiterate congregation repeats the lines of each hymn after they
  are read to them.


• Why there are no hymnals (most of the
  congregation can't read, and they can't afford them
  anyway).


• That at least one person (specifically Lula)
  does not appreciate the appearance of white faces at the
  church.


• That everyone else is respectful to
  them.


• That Reverend Sykes is quite persistent in raising
  the $10 collection to go to Tom Robinson's family.


• That
  they enjoy their visit with Cal so much that Scout wants to visit their housekeeper at
  her home as well.


• That people (be they black or white)
  are just people.