What are examples of characters being committed to justice in The Absolutely True Diary of a Part-time Indian?

In The Absolutely True Diary of a Part-time
Indian, Junior's math teacher Mr. P may be seen as one who commits himself to
justice.  When Junior gets Mr. P as his geometry teacher, Junior ends up being very
angry because Mr. P inadvertently gives him the same book that Junior's mother had at
the school nearly 30 years ago.  Junior throws the book at Mr. P because the school
obviously does not care much about the poor quality education that the students
receive.  Although he has gone along with the system for a long time, Mr. P comes to the
realization that the reservation is short-changing the students and that it is not
offering them a good education.  Mr. P goes to Junior's house to apologize for his role
in the failing system, and he encourages Junior to reach beyond the reservation to
follow his dreams.  Mr. P tells Junior that he will only receive any real opportunities
if he leaves the "rez."  In this way, Mr. P commits himself to justice--he admits that
he has been wrong for working in the system and gives Junior way out.  Mr. P believes
that this is the "just" thing to do.