What are the motifs in Children of a Lesser God by Mark Medoff?

Manipulation and control is a recurring idea. James is a speech therapist. He works with Orin and Lydia to improve their speaking skills. (He even corrects Orin's pronunciation of "sushi" when Orin expresses his anger that he too has eaten "hearing food.") James's job becomes convincing Sarah to speak. But Sarah has an agenda of her own, and does not place any value on learning to speak in order to appear "normal."