Why did tom sawyer sneak out of town

I'm not sure exactly where in the story you are referring to but I think it is when Aunt Polly learns from Sid that Tom snuck out the night before and cries over him. At school, Becky snubs Tom by paying no heed to his boyish antics. Hurt and angry, Tom assembles a "gang" of pirates: himself, Joe Harper, and Huck. The three boys decide that they have had enough of normal society and run away to Jackson Island, in the middle of the Mississippi River.