Check out the comments section after reading What 'To Kill a Mockingbird' Isn't in the Wall Street Journal. Jeezum Crow, people do not want anyone messin' with their Atticus.
To Kill a Mockingbird was one of the first adult books I read when in my early teens. I did not read it for school. This was before the schools got hold of TKAM, while it was still an adult book. I remember thinking it was quite an experience. When I reread it as an adult, years later, it seemed very much a father worship book to me.
I would really need to read it again before I'd describe it as a children's book. Do people get to take a vote and determine how already published books should be classified?
Again, this link came from ArtsJournal.