I call B.S. on the "but it's for kids" reasoning. I've never understood why kids should even read it. I guess people think it's for kids because it's Tom Sawyer's friend, but it's certainly not written for children. I don't think Twain expected kids even then to get all of his satire and references to pre and post Civil War American culture. I didn't really get the brilliance of it until late high school.