Wat is the theme of To Kill a Mockingbird?what are 3 quotes to support that theme

While there are many themes in almost every novel, there
is usually one dominate one.  In To Kill A Mockingbird, it would be lessons learned
growing up.  This broad theme includes many of the important life lessons Scout and Jem
learn as they mature.  For example, Jem learns that most of the people of Maycomb do not
share his father's opinions regarding race.  Before his family is threatened, Jem
believes that his neighbors are "good" people who will support Atticus and find Tom
innocent; however, most of the Finch family's neighbors are angry when it becomes
apparent that Atticus intends to actively defend Tom Robinson.  It is only with Miss
Maudie's help that Jem comes to understand that there are "good" people in Maycomb, like
Judge Taylor who appoints Atticus to the case because he knows Atticus will work on
Tom's behalf.  Scout comes to understand one of her father's most important life
lessons: you never really understand a person until you walk around in his/her skin. 
Scout learns to understand the actions of difficult people like her teacher Miss
Caroline, Aunt Alexandra, the Cunningham family, and even the malevolent Mrs. Henry
Lafayette Dubose.  Furthermore, when Scout stands on the Radley porch and views Maycomb
from Boo's point of view, she better understands him and why he chooses to remain in the
safe isolation of his home.  Most importantly, the children come to understand the
significance of Atticus' warning that it is a sin to kill a mockingbird.  When the
children receive rifles for Christmas, Atticus tells them they can shoot at other birds,
but not mockingbirds, for they do no harm; they simply make beautiful music.  That basic
description can be applied to both Tom Robinson and Boo Radley.  Tom helps Mayella Ewell
because he feels sorry for her, and that act of kindness leads to his death.  Boo Radley
risks his life to save Scout and Jem from Bob Ewell's vicious attack.  Sheriff Heck Tate
says that exposing Boo's heroic deed will thrust him into the limelight, thus shattering
his safe life of obscurity.  Because they have matured and witnessed the ugliest side of
human nature- hate, discrimination, envy, etc., they immediately understand the profound
significance of this statement.  In fact, Scout comments that there is not much else for
them to learn.  Thus, To Kill A Mockingbird is a novel about the lessons learned growing
up.