On Scout’s first day of school, she hits Walter Cunningham because Miss Caroline punished her for saying that the Cunningham’s don’t receive what they can’t pay back. Jem breaks them up and invites Walter to have dinner at their house and thinks that instead of fighting, Scout should treat Walter with respect.
Jem shows he’s maturing when he shows Scout he is growing chest hair and tells her he is going to try out for the football team. Another example is the night of the pageant in which he demonstrates his responsibility for protecting and standing up for Scout when Bob Ewell tries to kill them both. He took the risk to save his sister from the danger. At the end, Jem was unconscious, but Boo Radley came to save them. Jem was very brave to do this knowing he could die, yet he knew it was the right thing to do.