What was the purpose of mr.p telling junior about his sister's academic ability?

Mr. P tells Junior about his sister's academic ability to highlight the importance of education and to encourage Junior to pursue his own potential. He reflects on how, despite her intelligence, she was limited by her circumstances on the reservation. By sharing this, Mr. P aims to motivate Junior to break free from the constraints of his environment and strive for a better future. It serves as a pivotal moment for Junior, reinforcing the value of education in overcoming adversity.