How do Scout and Jem from To Kill a Mockingbird symbolize a mockingbird?

The mockingbird is a symbol of innocence in the novel:
Atticus and Miss Maudie explain that the birds don't harm gardens or "nest in
corncribs;" they only sing and make people happy. Like a mockingbird, children are
generally a joy for most people, free from committing the sins that come with growing
up. Atticus' warning to Jem about shooting a mockingbird is not heeded by all people,
and some shoot them for fun; Bob Ewell's attempt to harm Jem and Scout is a parallel to
such actions. The innocence of Jem and Scout remains throughout the story, though
they witness actions that are far from innocent: The Ewells accuse an innocent man of
terrible crimes; the jury condemns Tom Robinson in spite of evidence to the contrary;
racism is seen among churchgoers and teachers; and they are attacked by a man who seeks
revenge on a man by killing his children. Yet in the end, the children survive, and
their neighbors will continue to enjoy them for the remainder of their days of
innocence.