One day on the bus, May Belle makes the mistake of shrieking across the bus to a friend that her father gave her Twinkies in her lunch. Unsurprisingly, Janice Avery steals May Belle's Twinkies at lunchtime. May Belle immediately runs screaming to Jess, demanding that he beat her up. Jess is loath to do so, since Janice is a lot bigger than he, but May Belle insists that he is "just yeller" and that a good big brother would beat her up. Leslie intervenes and tells May Belle that she and Jess will find some other way of getting back at Janice, explaining that the principal will kick Jess out of the school if he's caught fighting a girl. Jess gratefully agrees.
In Terabithia, they come up with a plan: they write a love letter to Janice from Willard Hughes, the boy every girl in the seventh grade has a crush on. The letter says that Willard is madly in love with Janice and wants to walk her home from school the next day. The next day in school Jess slips it into her desk. Sure enough, Janice falls for it, and misses the bus the next day, only to have to walk home alone when Willard obviously does not show up. Jess feels a little bit badly for her, but feels they could not have done anything else. The next morning, Janice is furious, and May Belle is thrilled to know that her brother did so much for her.
Janice's status as school bully is odd, given that that it is generally understood to be a masculine role. In some ways, Janice and Leslie are alike, since both flagrantly defy gender stereotypes. The effect of this scene is also to flesh Janice out a bit, and give her a little bit more of an individual personality. This will become important later in the novel, when Jess and Leslie get to know her in a different light.
Jess's willingness to risk his own safety to get revenge on Janice Avery demonstrates that he truly cares about May Belle. She is the only member of his family who is generally shown in a positive light. She is certainly not idealized, as she gets on Jess's nerves quite often, but she is still generally depicted as a "good kid." Jess's revenge on Janice Avery shows that he is capable of intense loyalty and caring, not just to Leslie, but also to his family. Writing that note to Janice Avery was an act which required a good deal of courage, knowing what Janice would do to them if she found out and it says a lot for Jess that he's willing to do it.
Jess's treatment of Leslie proves that he is not "yeller," as May Belle says. The way things turn out is another demonstration that society's expectations of boys and the "masculine" way of dealing with problems is by no means always the best. May Belle admits, when she demands that Jess fight Janice, that "she'll beat him up," yet she feels this is the way Jess has to deal with it and she is incapable of imagining a less violent solution. Jess himself very nearly capitulates and agrees to fight her, even though he knows it will not do any good and that Janice will emerge triumphant. Once again, though, it is Leslie who saves the day and shows Jess that he does not always have to do what his classmates assume is the right thing for a boy to do. Their solution requires cunning, stealth, and intelligence, rather than just brute force, and is ultimately far more successful than a fistfight would have been.