The terms turning point and climax are used interchangeably as literary terms. A turning point, or climax, is the moment in the story when "all rising action turns around into falling action" (Literary Devices, "Climax"). At this moment, the conflict has reached its greatest point of intensity, and the resolution is in sight. There are two major plot-lines within Harper Lee's To Kill a Mockingbird. The first concerns the children's coming-of-age story, which entails learning acceptance. The second concerns Atticus's role as Tom Robinson's defense lawyer, which has significant consequences for the children and plays a crucial role in the children's development. Both of these plot-lines have their own major turning points.
The most important factor in the children's coming-of-age story is their learning to accept Arthur (Boo) Radley. Jem is the first of the children to realize that Arthur is not the monster they think he is. Jem develops this realization as he comes to understand that Arthur is reaching out to the children and showing kindness in his own quiet way by mending Jem's pants and leaving the children gifts in the knothole of an oak tree on the Radleys' property. He is so moved by the kindnesses and feels so ashamed of having mocked Arthur that he cries by the end of Chapter 7. As Jem further comes to understand how different people can be and to accept those differences, he comes to understand that Arthur stays in his house all the time simply because "he wants(it) to stay inside" (Ch. 23).
However, the greatest moment of turning point concerning the children's coming-of-age story doesn't occur until Scout has her own epiphany at the very end of the book. By the end of Chapter 29, Scout realizes two things. First, she realizes that as she looks at the strange man standing in her brother's room, she is looking at her neighbor Arthur for the very first time. Second, she realizes it was Arthur who saved the children's lives. Seeing her previously mysterious neighbor as their caring savior moves her to tears, just as Jem had been moved to tears earlier. Her greatest moment of epiphany is revealed in the final chapter when she says she has finally come to understand what Atticus means when he said, "[Y]ou never really know a man until you stand in his shoes and walk around in them" (Ch. 31). Standing on Arthur's porch after having escorted him home, she feels she is able to see things as Arthur saw them and understand how much he cares about the two children.
The turning point in Atticus's case defending Tom Robinson occurs the moment Robinson is found guilty by the jury. Though Atticus revealed a great deal of circumstantial evidence proving Robinson's innocence and has every hope of Robinson being acquitted upon appeal to the higher courts, Robinson's fate is sealed at that point. His fate is especially sealed the moment he tries to take justice in to his own hands by attempting to escape prison and is shot to death by the prison guards. These events force the children to understand the injustice in the world, an understanding that helps them grow up.