What part does the English teacher play in this part of the book? Who is he? Why do you think Capote includes him?

Nancy's English teacher is named Mrs. Riggs. Her part in the novel helps to illustrate Nancy's youth and innocence.

Once Mrs. Riggs, her English teacher, had returned a theme with a scribbled comment: "Good. But why written in three styles of script?" To which Nancy had replied: "Because I'm not grown-up enough to be one person with one kind of signature."