Jem plays the role of a typical big brother here. He is prepared to run out the door and join his friends on the first day of school, but Atticus makes him sit down for breakfast and wait for his younger sister. Jem lets it be known he is not looking forward to towing his younger sister along on his first day.
However, he quickly takes advantage of his senior role around school. He feels like the experienced big shot in terms of how school works and the expectations of his teachers and friends. Like most big brothers, we will see him share his "knowledge" of how things really work at school with Scout as the story progress, but he is often humorously incorrect with the younger Scout none the wiser. For instance, he speaks (incorrectly) of the intricacies of the Dewey Decimal system stating, "I'm just trying to tell you the new way they're teachin' the first grade, stubborn. It's the Dewey Decimal System (Lee 18). Scout describes for the reader that, "The Dewey Decimal System consisted, in part, of Miss Caroline waving cards at us on which were printed "the," "cat," "rat," "man," and "you" (Lee 18).