What was the "code of childhood" according to Scout?

One night shortly before the Tom Robinson trial began, Scout stepped on something in her room that she thought may have been a snake. When Jem came in to investigate, he found it was not a reptile, but Dill hiding under the bed. Dill had run away from home and taken a train and then walked to Maycomb. He was dirty and hungry. He told his tale of woe: His father hated him and bound him in chains in the basement. He had to eat raw peas to survive. After absorbing his story, Jem "rose and broke the remaining code of our childhood." He ratted out Dill to his father, Atticus, and betrayed their childhood trust. Of course, Jem knew that Atticus would treat Dill fairly, and after notifying Aunt Rachel, a call to Dill's parents assured him a longer stay in Maycomb.