In To Kill A Mockingbird, Jem changes throughout the novel. First of all, Jem is a young boy who plays games with his sister Scout and Dill, a neighborhood friend. He is immature in the beginning, "allowing Scout to join in his games and even dignifying her with an occasional fistfight."
He is not as concerned about things. Jem does not appear to have the temper that Scout has. Jem seems laid back.
As the story progresses, Jem grows up. Jem begins to only want to spend time with Dill. Jem out grows the desire to allow Scout to play. Jem and Dill go swimming without Scout. Scout feels left out, but Jem doesn't seem to care.
Also, as Jem matures, he becomes more concerned with the racism that his father is dealing with during the trial. During the trial, he sees hatred and bigotry in all its unfairness. Also, he loses his temper when Mrs. Dubose insults his father as they pass her house. Jem retaliates and beats all the buds from Mrs. Dubose's flower bushes:
As he approaches adolescence, however, Jem becomes quieter and more easily agitated: he reacts angrily when Mrs. Dubose leaves him a small peace offering after her death.
Also, Jem doesn't want to disappoint his father. "He is anxious to please his father, and hates to disappoint him."
Jem is truly troubled by what is going on in Maycomb. He realizes that a man's life is being threatened because he is black. During the Tom Robinson trial, Jem realizes the injustice of a man not getting a fair trial because he is black.
Jem has grown up to be more concerned for his family's safety. Jem also has to protect his sister when they are attacked by Bob Ewell. Jem stands up for his sister. Jem has grown into a fine young man who realizes some things are worth fighting for:
He demonstrates his own courage, however, when he protects his sister from the attack of Bob Ewell without regard for his own safety.
Still, he learns from his father that some battles are lost before one begins fighting, but still one must persevere and fight on. Hopefully, change will occur one day.
No doubt, Jem changes during the course of the novel. He begins as a boy who plays games with Scout and Dill. By the end of the novel, he has grown into a adolescent who "has weathered turbulent times."