How does Junior change throughout the story and how does he grow?

As the novel is a bildungsroman (coming of age story), Junior experiences many moments of change and growth throughout the book. One huge change Junior makes is realizing that even though he has been an outsider in many ways his whole life, he is also a part of "many tribes."  After a lifetime of bullying from his fellow tribe members and racism from his teachers and peers at Reardon, it's understandable for Junior to feel like an outsider in both worlds and like he doesn't fit in anywhere. As he deals with these problems throughout the story, though, he comes to a realization:

"sure, I was a Spokane Indian. I belonged to that tribe. But I also belonged to the tribe of American immigrants. And to the tribe of basketball players. And to the tribe of bookworms.

And to the tribe of cartoonists.

[...]

And the tribe of funeral goers.

And the tribe of beloved sons.

And the tribe of boys who really missed their best friends.

It was a huge realization.

And that's when I knew that I was going to be okay" (pg 190)

Junior discovers that you don't have to fit into a certain stereotype or group; it's enough to build your own groups of people, with all the little or big things you have in common. 

Another big change Junior makes is his decision to actively work for the future he wants. Junior has always known how the reservation holds little hope for a good future. He's seen his parents and sister give up on their dreams. He doesn't want the same thing to happen to him. So when he gets his mother's old textbook at school, he really feels the threat of losing his optimism and hopes and dreams on the reservation:

"And let me tell you, that old, old, old decrepit geometry book hit my heart with the force of a nuclear bomb. My hopes and dreams floated up in a mushroom cloud" (pg 34).

It is this event that leads Junior to the decision to attend Reardon and work to get a better education and more opportunities. At the end of the book, he has only completed his freshman year at Reardon, but already he seems more hopeful about the potential future he can have. 

Finally, an area of growth for Junior is in his social-emotional intelligence. It's natural for Junior, as someone who has been bullied a lot, to judge people harshly and see the bad sides of them. What's impressive in the novel is how forgiving he can be, and how perceptive in seeing other sides of people. Even though Penelope mocks him and Roger says one of the most racist jokes in a middle grade book, the two still end up two of his close friends by the end of the year. Of Roger, Junior says he is "of kind heart and generous pocket and a little bit racist" (pg 119). In Penelope's case, Junior goes back and forth seeing her deep dreamer side and her superficial pretty side, but also recognizes his own shallowness in doing so. In discovering that humans are nuanced, with both good and bad sides, Junior matures in how he relates to others.