Who is the antagonist of eleven by Patricia Reilly?

There isn't a single, clear-cut antagonist in Patricia Reilly Giff's *Eleven*. The story focuses more on the internal struggles and anxieties of the protagonist, Rachel, and the challenges she faces from the cumulative weight of her experiences and perceptions of her environment.

While Mrs. Petosa (her teacher) is the source of some immediate conflict, she's not a traditional antagonist in the sense of actively working against Rachel for malicious purposes. Her actions stem from a lack of understanding and empathy rather than deliberate cruelty. The real antagonist could be considered Rachel's own insecurities, anxieties, and the pressures of growing up.