Can anyone explain the significance of the black community and the black church in the novel a Lesson Before Dying

At the beginning of the novel, Grant views religion with disdain, acknowledging its important place in African-American culture while questioning its truth and its usefulness. Although he never embraces Christianity, the events of the novel make him more aware of how religion can soothe the afflicted. He encourages Jefferson to pray just to please Miss Emma, also suggesting that religion can be a useful means of social cohesion even if the teachings themselves are questionable to some. 

As for race, racism pervades the ethnically mixed town of Bayonne.This is a fact that might not surprise those familiar with the history of the South at this time. However, Gaines also portrays racism within the African-American community in the quarter. Mulattos avoid associating with full-blooded African-Americans, and Grant himself harbors some negative stereotypes about mulattos, speculating that they all work in bricklaying so they don't have to be around full blacks. The women who are considered beautiful in the quarter all seem to be light-skinned. Gaines takes care to emphasize that anyone can be racist, without minimizing the enormity of segregation by whites.