When we think of class, we usually think of economic class—you know, who's got the Benjamins and who doesn't. And sure, that kind of class plays a role in The Watsons Go to Birmingham—1963. After all, a lot of the bullying that goes on at Clark Elementary is based on money. But elementary school has a class system of its own, and who gets bullied and who does the bullying depends on each kid's place on the social ladder. Any little thing that different about someone is exploited as a weakness by the school bullies. This is an issue that Kenny struggles with throughout the book; and eventually, Kenny's questions resonate with even bigger questions about the violence and hatred of racism.
If Kenny were a bully like Byron, he would have a higher place on the social ladder and wouldn't get picked on.
Relative wealth is the most important factor in determining social status at Clark Elementary.