In a uniquely powerful manner, I think that we can find examples of specific characters' intellectual competencies in one moment. When Junior lashes out at Mr. P because of anger over receiving the same textbook his mother had received, it is a moment in which "something" has changed within Junior. The discussion that Mr. P has with Junior is one that reveals his sister's intellectual competence and Junior's.
Mr. P confesses to having made mistakes as a younger teacher. He tells Junior that when he first began to teach on "the Rez," he was ..I was young and stupid and full of ideas." It is in this confessional moment that Mr. P talks of Junior's sister. Mary demonstrated intellectual competence through her writing. Mr. P remarks that Mary was "the smartest kid (he) ever had." Her intellectual competence is something that Mr. P relays was so strong that Mary was afraid of being mocked by others. In this, Mr. P suggests that Mary was "a bright and shining star" whose lustre "faded year by year until you could barely see her any more."
It is here where Junior's own intellectual competance can be seen. At this moment, Junior realizes that he must leave "the Rez." Junior takes Mr. P's words to heart in recognizing that there is no future for Junior living on the reservation. It requires an intellectual competence to project in the future and examine the arc of his intellectual trajectory. Junior recognizes that there will be no advancement of this if he stays at Wellpinit. Junior's intellectual capacity is one where he does not lose sight of the "fierce urgency of now" of which Mr. P speaks. It is intellectual capacity that permits him to understand that he does not want the same fate that visited his sister to happen to him.