Answer:
The bus driver purposely slung dust and mud onto the children as it passed, as a way to insult the Logan children and T.J, since they were black people.
Explanation:
The children laugh as they pass the children, and later on, T.J comes up with a plan to make their foolery end (I won't spoil...). Little Man gets very upset, as the dust gets him dirty, and he throws a fit.
