In the novel, To Kill a Mockingbird, how does Jem break the remaining code of childhood?

In Chapter 14, Jem broke the remaining code of childhood by telling Atticus that Dill had run away from home and was hiding under Scout's bed. As Scout was climbing into bed, she stepped on something that she thought was a snake. Scout beckoned Jem to come and check it out. Jem grabbed a broom and began to poke underneath Scout's bed. Surprisingly, Dill emerged from under the bed. Scout and Jem were shocked to see Dill, and he told them a made-up story about how he escaped from his parent's basement in Meridian. Jem then made Dill tell them how he truly traveled to Maycomb. Dill said that he took $13 from his mother, rode a train, then walked the rest of the way to Maycomb. Jem displayed his maturity and growth by telling Atticus that Dill had run away from Meridian. Scout and Dill were upset at Jem for telling Atticus. Scout mentioned that Jem looked like a "traitor" and that she and Dill did not speak to Jem when they left the room.