Bob Ewell has many children, but one son in particular is mentioned during the first day of school for Scout. If you look closely at chapter 3, we are introduced to many young children, through Scout, as she goes to school for the first time. In these introductions, we learn quite a bit about the attitudes, prejudices, gossip, and history of the town of Maycomb and the surrounding counties. Scout herself takes it upon herself to help enlighten her rather naive teacher, Miss Caroline, on the intricacies of Maycomb social classes.
Bob Ewell's son, Burris, comes to school that day, and it is the only day out of the entire year that he comes. The truant officers at the school bully the Ewell children into coming to school for at least one day so that they can be on the school rolls--this keeps the sheriff and others off of their backs about getting the Ewell kids to school. But, they can't keep them there long. So, Burris, who is there the first day, probably won't be seen again. We get a rather colorful description of him too; Scout says that "he was the filthiest human being I had ever seen," and after a confrontation with Miss Caroline about washing his hair, she asks him to leave. He complies, and leaves, not to be seen at school again that year.
I hope that helped a bit; good luck!