The novel's examination of race revolves around the character Jimmy and the sandwich shop he owns where Miranda, Colin, and Annemarie work during their lunch period.
We learn very early on that not only is Jimmy a little weird for giving a bunch of sixth graders jobs as sandwich makers (Chapter 15), but he also holds offensive views about different races. Jimmy does an impression of an Asian American, for example, in which he stretches "his eyelids back with two fingers" and gives a low bow (18.2). We know that the novel sees this attitude as prejudiced and offensive because Miranda notes that she had had never seen a grown-up act like Jimmy, and that if her mom had seen him do the impression, "she would have whacked him on the head with a plastic tray" (18.2). Miranda's mother acts as Miranda's moral compass; she provides a major contrast to Jimmy's ignorant attitude.
While we could argue that Jimmy's impression, while totally stupid, is relatively harmless, we see the larger implications of his racist worldview in his dealings with Julia. Jimmy is always throwing Julia out of the store, accusing her of theft, or using Miranda's nickname for her, "Swiss Miss." Jimmy uses the phrase not as a reference to Julia's many trips to Switzerland, but as a derogatory way to describe her dark skin. Even after Annemarie explains to Jimmy that Julia's family has plenty of money so she doesn't need to steal, Jimmy holds fast to his warped and racist beliefs by saying that some things are "in the blood. All the money in the world can't change a person's blood" (37.9-14).