At the beginning of the story, we see Stanley as a quiet, passive kid who is prone to being bullied and taken advantage of. He simply accepts his sentencing to Camp Green Lake and goes with absolute compliance (even though he did not steal the shoes).
Stanley was not a bad kid. He was innocent of the crime for which he was convicted. He'd just been in the wrong place at the wrong time.
We see this compliance follow him to camp, where he conforms to the expectations set by the warden. However, as the story progresses, we see Stanley take more control over his emotions and recognize his importance as an individual. Stanley is able to unveil the truth about Kissin' Kate Barlow's treasure (stolen from Stanley's relative, Elya). While uncovering this truth, Stanley also reverses his family curse when he carries Zero (a descendent of Madame Zeroni) up the mountain. With this act alone, he proves his bravery and compassion toward his friend.
Stanley Yelnats learns that he is more than just an unlucky kid. He learns that he is actually capable of redeeming himself and his entire family. Although his family is cursed, Stanley is the one who breaks this curse. In the end, Stanley has fulfilled his role as a dynamic character. He leaves behind the insecure, overweight child and becomes a man.