What are some ways that Tom Sawyer grows up in The Adventures of Tom Sawyer by Mark Twain?
Tom Sawyer demonstrates maturity when he takes a whipping for his torn spelling book. Later, he takes the blame for ripping a page of Mr. Dobbins's anatomy book. Tom committed neither of these acts. Later, Tom courageously testifies against Injun Joe in defense of Muff Potter.
Tom demonstrates moral strength in chapter 20 when he takes the punishment for spilled ink on the spelling book, even though he has not done the damage to this school book. When he returns to his seat, Tom starts to think that he may have upset the ink upon the spelling book. Becky Thatcher keeps quiet about Alfred Temple having done the damage because she is angry with Tom. After an hour, Mr. Dobbins unlocks his drawer and pulls out his treasured anatomy book to read it. Tom glances at Becky, knowing that she has previously removed the book from the drawer and has torn a page in her hurry to replace it. When he sees Becky looking like "a helpless rabbit," Tom forgets his quarrel with her, and he considers grabbing the book and running out the door. Unfortunately, it is too late. "Who tore this book?" Mr. Dobbins demands. He calls on each student until Tom shouts, "I done it!" to protect Becky. Tom takes
Without an outcry the most merciless flaying that even Mr. Dobbins had ever administered (Ch.20).
It is worth the whipping to him when Becky says, "Tom, how could you be so noble!" (Ch.20).
In chapter 23, Tom's decision to come to the defense of Muff Potter at his trial marks the attainment of moral courage in Tom; although he is still in fear of Injun Joe, he feels he is obligated to reveal the truth. Tom puts aside his fears and his superstitions about the blood oath that he has sworn with Joe Harper not to tell. Instead, Tom testifies in court that he hid behind trees on the edge of the grave. Tom further reveals that he witnessed Injun Joe brutally stab Dr. Robinson after Muff was knocked unconscious. When this is said, Injun Joe springs for a window and is gone. However, Muff Potter is acquitted.
There is one clear moment of change, and that is at the end of the novel, when Tom urges Huck to stay with the widow Douglass and submit to proper clothes, Sunday school, and other conventions of society. At the beginning of the story, Tom envies Huck for his freedom from these very same things:
"Huckleberry came and went, at his own free will. He slept on doorsteps in fine weather and in empty hogsheads in wet; he did not have to go to school or to church, or call any being master or obey anybody; he could go fishing or swimming when and where he chose, and stay as long as it suited him; nobody forbade him to fight; he could sit up as late as he pleased; he was always the first boy that went barefoot in the spring and the last to resume leather in the fall" (Chapter 6).
Tom is envious of Huck's freedom from the rules and expectations of society that Tom is always getting in trouble for breaking. At the end of the novel however, when he encourages Huck to stay with widow Douglass, he has clearly changed into someone who helps to enforce society's rules and expectations. Still, when Tom says,
"But Huck, we can’t let you into the gang if you ain’t respectable, you know" (Chapter 35)
It's clear that despite that change, some of Tom's mischievous manipulations remain. Still, Tom has grown up and, for him, being an adult means leaving behind childish freedom and conforming to society, at least somewhat.