What new things do Scout and Jem learn about how the black people at Calpurnia's church?In chapter 12.

They learn that Calpurnia's congregation in To
Kill a Mockingbird are human beings, no different than most others. Although
it is unusual to see white faces in the church, Jem and Scout are treated well. They
initially have a run-in with Lula, who objects to their presence, but they are made to
feel at home for the remainder of the service. The children learn that the congregation
is poor and mostly illiterate; there are few hymnals since they can't afford them and,
besides, most of the members cannot read. So, Calpurnia's son, Zeebo, leads them in
"linin'": he reads the line, and the congregation repeats it. The children also find
that the members are supportive of Tom Robinson. Although they are quite poor, the
collection plate--actually, a coffee can--is passed around repeatedly until Reverend
Sykes determines that enough money ($10) has been collected. In the end, Jem remarks
that Reverend Sykes is "just like our preacher."