Why is Duddy suspended from parochial school in "The Apprenticeship of Duddy Kravitz?"
Duddy starts life out as a bully. Determined to be successful from a young age, he does not mind the methods needed to obtain money, power, and prestige. At school, he gets all through the Warriors. This group of boys establish themselves as the "top" group, the most powerful group in school. Be a part of the group, and you could have access to friendship, popularity, money-making opportunities - you name it. Be outside the group, and you were subject at any time to be pushed around.
Duddy eventually gets suspended when he wields the power of the group against classmate Milty. Knowing that Milty is desparately eager to get into the group, Duddy convinces Milty to drink a "potion". After Milty does, Duddy claims it was the wrong potion. Not only does Milty not get into the group, but Duddy threatens that this potion will prevent him from "growing a bush."
When Milty cries to his mother, she sees the headmaster and Duddy is suspended - however, this doesn't prevent him from continuing to wield control over Milty, bullying him in his own home. The fact that he still has this control demonstrates the price and the negative power of success and popularity. These incidents also foreshadow Duddy's later betrayal of people who love him.