The Magic Mean Machine — Beatrice Gormley

How can Alison Harrity beat bully Spencer Cunningham? Alison would have a good chance to win the fifth grade chess tournament -- except that Spencer is cheating his way to the championship. And Alison isn't pushy enough to stand up to him. Then Marvin Smith, a science wiz, invents the DISAST to help Alison get really tough. But is it worth it to win the tournament, if she loses all her friends?