Explain why this is truly the story of Jem maturing more than Scout.The story is an exapmle of bildungsroman, a coming of age story, or the story...

While Scout narrates the story, To Kill a
Mockingbirdclearly shows Jem's actual maturing more than Scout's. Several
examples of his growth and development are clearly seen throughout the novel.  Jem is
the one, during the trial, who both understands the issues of the case but also the
implications of the verdict.  He is fully aware, in a way Scout is not, of Tom's
innocence and the injustice which is done when the guilty verdict is returned.  Jem is
visibly shaken and emotional when the trial is
over. 

Later, in chapter 22, Miss Maudie recognizes this
growth in Jem and serves him from the grownup cake rather than giving him his own small
cake like Scout and Dill get--a hugely symbolic gesture to these kids.  She goes on to
speak with him about the trial as if he were an adult.  In that conversation he
says:

"It's
like bein' a caterpillar in a cocoon, that's what it is," he said.  "Like somethin'
asleep wrapped up in a warm place.  I always thought Maycomb folks were the best in the
world, least that's what they seemed
like." 

He has been
disillusioned in a way that robbed him, to some degree, of his innocence.  Even the
cocoon reference is a picture of maturing and growing. 

Jem
is also Scout's comforter (rather than her tormentor) when Scout's convinced Aunt
Alexandria hates her.  He hands her a tootsie roll, a very unselfish act, to help her
get past the tears.  Then he expounds on something he's been thinking, something which
also reveals his new-found maturity:

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"You know something, Scout?  I've got it all
figured out now.  I've thought about it a lot lately and I've got it figured out. 
There's four kinds of folks in this
world." 

He goes on to share
some insights which reveal his ability to discern human nature--a sure sign that Jem has
grown up.

Other moments (among many) along the way include
retrieving his torn overalls from under the Radleys' fence, the episode with Mrs.
Dubose, and the night in front of the jailhouse.  Don't be fooled by Scout's insights
along the way; this is primarily Jem's emotional journey.