August tells the reader some of the names that kids call him: rat boy, E.T., lizard face. He runs to the bathroom, cries for a while, and then goes to the nurse's office and tells her that he has a stomachache. She calls Mom and fifteen minutes later, Mom arrives to pick August up. August just tells her that he feels sick; he doesn't want to tell her the truth at school. The nurse helpfully offers that there's a stomach bug going around. Mom and August walk home with their arms around each other and later, August says he's too sick to go trick-or-treating. He doesn't go to school the next day either, and thinks he won't go back at all.
August's reaction shows that Jack had earned August's trust by being one of the only kids to treat him kindly—and it's that broken trust that makes this situation so painful, since August is clearly aware that other kids regularly call him names. The fact that August doesn't want to go back to school after this incident shows how just one person, whether they know it or not, has the power to deeply impact a classmate's life.