Jem decides that what he and Scout and Dill did (trying to peek in Boo Radley's house) is wrong. Why do you think Jem feels this way? What was so...

Although the narrator of To Kill A Mockingbird is Jem's sister Scout, the character who seems to show the most personal growth is Jem.  The action of this story takes place over two summers when Jem is at an age when boys begin to outgrow childish activities and begin taking on responsibilities as young men.  In many instances throughout the book, we see Jem standing up for Atticus, and sometimes standing up TO Atticus as...

Although the narrator of To Kill A Mockingbird is Jem's sister Scout, the character who seems to show the most personal growth is Jem.  The action of this story takes place over two summers when Jem is at an age when boys begin to outgrow childish activities and begin taking on responsibilities as young men.  In many instances throughout the book, we see Jem standing up for Atticus, and sometimes standing up TO Atticus as well, as he is learning to take on some independence.  Sometimes, however, the "boy" part of Jem and the "young man" part of Jem come into conflict with each other, and your question highlights one of these episodes.

Jem, Dill and Scout treat Boo Radley as an object of fascination.  They do not see him as a real person with thoughts and feelings, but rather as a kind of mysterious monster.  With this in mind, they try to peek in the window of the Radley house to see what Boo looks like.  They realize that Atticus would not approve, so they sneak over at night.  They are startled by Mr. Nathan Radley, Boo's father, and narrowly escape without getting caught.

In reviewing the incident later, Jem comes to a realization that perhaps they shouldn't have been doing that in the first place.  This illustrates Jem's growing up.  Partially, he is coming to understand Atticus's thinking in telling the children not to bother Boo Radley, and partially he is reaching that realization on his own: Boo Radley is, in fact, a person to be respected.  The simple act of looking in a window is not really "so wrong," but the way that the children think of Boo is wrong, and Jem is learning this lesson before Scout and Dill.