In what way could the end of Chapter 9 be considered the turning point in the novel?
I think that a case can be made that chapter 9 is a sort of turning point in the novel because it represents the final dissolution of the friendship between Amir and Hassan. It is at this point where their friendship ends up becoming interrupted. It is also at this point where Amir's cruelty becomes its most intense. To frame Hassan for stealing in addition to all that has happened is both a statement of Amir's cruelty as a child and both Hassan's absolute loyalty in how he accepted responsibility, knowing the truth. In chapter 9, one sees how this friendship disintegrates under the weight of social malignment as the social differences between both boys becomes a pretext why Amir's lies can be accepted with so much ease. It is also the point where Amir feels the most amount of guilt. It becomes a weight that is forgotten for a while, but something that is always there. The rain that permeates his vision while he sees his father drive Baba and Hassan to the station does not obscure the guilt that is always there. It is from this point that one understands why exactly he feels compelled as an adult to do what he must do. It is for this reason why a turning point can be seen at the end of chapter 9.
At the end of Chapter 9, Amir sets up Hassan by hiding his presents underneath Hassan's bed to make it seem like Hassan stole them. Despite Baba's willingness to forgive Hassan, Ali and his son pack their things and leave the household. This moment could be considered the turning point in the novel because it is when Amir and Hassan's friendship permanently breaks and seems to be irreparably damaged. Also, it is possibly Amir's most deplorable action and Hassan's most loyal moment in the entire novel. Amir can no longer look at Hassan anymore because of his guilt, which is why he chooses to falsely accuse Hassan. However, this only adds to Amir's guilt and seems to end their long friendship. Shortly after Ali and Hassan leave Baba's household, Amir and Baba escape Afghanistan and immigrate to America. Amir has no contact with Hassan, and their friendship seems to be irreparably damaged. Fortunately, Amir learns from Rahim Khan that Hassan has forgiven him and has longed for Amir's friendship.