How is Tom a "hero" again?

Ridden with guilt, Tom apologizes, but tells Polly that he had meant to give her the piece of bark. Confused, Aunt Polly asks Tom: "Did you kiss me, Tom?" Upon hearing him admit that he did so because he loved her, she forgives him and sends him off to school.

After Tom leaves the house, she reaches for his jacket pocket to find the piece of bark with Tom's handwriting scrawled across it. Reading his message, she cries: "I could forgive the boy, now, if he'd committed a million sins!"