The motif to which the novel owes its name is a major structuring motif for the narrative. The fourth grade rats rhyme opens the novel: “First grade babies! Second grade cats! Third grade angels! Fourth grade…RAAAAATS!” (1). In the context of the story, the rhyme is meant to dictate the students’ social hierarchy, which is predictably based on age. Characters like Joey take the rhyme very seriously and use it as a guide to behavior. The motif of the rat is a device that Jerry Spinelli uses to represent the transition from childhood to preadolescence, thereby forcing the main characters to question the essence of their shifting identity in this new context. Suds’s desire to become a rat drives many of his decisions in the novel, and Spinelli therefore uses the motif of fourth grade rats to portray the complex challenges of growing up.

The fourth grade rats rhyme represents the social pressure to conform to a troublemaking identity. Becoming a rat is the mechanism through which Suds confronts important ideas about growing up, and he undergoes many unforeseen challenges as Joey encourages him to leave things from his childhood behind and to embrace problematic behavior that contradicts his values and temperament.