We learn at the beginning of Chapter Ten that Atticus is considerably older than most of the other kids' fathers in Maycomb--he is almost fifty years old. Because of his age, and his personality as well, Atticus can't (or won't) do many of the things the other fathers do. He won't play football with Jem, he doesn't hunt, and for that matter, he doesn't drink or smoke. "He sat in the livingroom and read," Scout tells the reader (92). Miss Maudie tries to make them understand that their father is a wonderful lawyer and, she adds, very good at checkers. It seems that the children are a little embarrassed by their father, and they wish he was, for lack of a better word, cool.
They are surprised, then, at the end of the chapter when Atticus returns home to shoot a rabid dog in the street. In fact, Sheriff Tate gives him his rifle because he knows what the children do not--that Atticus once was, and apparently still is--the best shot in Maycomb. He proves this when he takes the mad dog down with a single shot to the head. With this, Jem in particular is suddenly very proud of his father.