What is an example of metaphor in the novel, The Heaven & Earth Grocery Store?

The author metaphorically compares Bernice and Chona to robins and sparrows as a symbol for the dismissive brand of systemic racism that prevails in Pottstown's schools. A teacher seeks to sow discord between Bernice and Chona, who are old friends, by uplifting Chona's insights, skills, and musical talent over Bernice's comparable or better performance of the same things, insisting that Chona sounds like a robin and Bernice sounds like a sparrow. Chona's insistence that Bernice is in fact a robin stands in for her love for her friend and her regret over their arbitrary and hateful separation from one another.