Little Chuck Little & Burris Ewell are presented as foil character-polar opposites. Why is this true?

Chuck and Burris each come from very poor families, but they are also being raised in completely different ways. Walter is prideful as a result of his family's values, but he is also dirty and disrespectful. Chuck defends Miss. Caroline from Burris' flood of insults and demonstrates the positive values that Burris lacks.