Mr. P is the white teacher at whom Arnold throws the geometry book. But instead of being super-miffed and maybe even throwing the geometry book back, Mr. P convinces Arnold that he's a fighter and has to leave the reservation to get a better education.
"If you stay on this rez," Mr. P said, "they're going to kill you. I'm going to kill you. We're all going to kill you. You can't fight us forever."
"I don't want to fight anybody," I said.
"You've been fighting since you were born," he said. "You fought off that brain surgery. You fought off those seizures. You fought off all the drunks and drug addicts. You kept your hope. And now, you have to take your hope and go somewhere where other people have hope."
I was starting to understand. He was a math teacher. I had to add my hope to somebody else's hope. I had to multiply my hope.
"Where is hope?" I asked. "Who has hope?"
"Son," Mr. P said. "You're going to find more and more hope the farther and farther you walk away from this sad, sad, sad reservation." (5.163-5.168)