I would say that the rising action occurs when By is set by his parents to Burmingham to live with his grandmother . This move sets the stage for the action that is to follow, that is, moving By away from himself and his narrow world and locating him into the consciousness of the civil rights movement.
Here is an excerpt from the "overview" page here at eNotes that should help you identify the rising action (climax) and the falling action (denouement) that follows:
"Dad and Momma, as the Watson children call their parents, are determined to raise respectful, well-behaved children who make good choices and possess high moral standards. Realizing they have been unable to instill fully their standards in their oldest child, Dad and Momma decide to take By to Birmingham and leave him with his Grandma Sands, a strong woman who will bring him to his senses. They know there is some violence in the South with the beginnings of the Civil Rights Movement, but have been assured by Grandma Sands that it is quiet around her."
The Rising Action is the actions or events that occur that
lead up to the climax.Where the suspense builds up and the
character struggles to find a answer to the problem. Its when
the conflict begins to unfold as the plot becomes more complex and problems and complications arise.
example: In Harry Potter and the Sorcerers stone, Harry Potter must go through a set of tasks to reach where the Sorcerer Stone is hidden, where he will have the final battle. These are the actions leading up to the climax where Harry must face the thief who is trying to get the stone.