Bridge to Terabithia
Jess fits perfectly into the role of the protagonist. The whole story is told from his point of view, and he's the good guy, wouldn't you say? Even when he makes poor decisions, readers can still find him sympathetic. He has struggles to overcome and battles to endure (both internal and external), and along the way he experiences love and loss. Although he's still only a fifth grader when the story ends, in many ways he's grown up. We can see the kind of man he's going to be, and it's a good one. He'll be able to reach beyond the limitations his family and class have on him, and follow the path that Leslie laid out for him. It sounds as though he's learning to become a guide/mentor himself.