Literature edited specially for children?

Hi All,
I'm a computer scientist and I need your expertise so much.
I'm looking for literature that has BOTH adult version (or normal version) and children version (up to high schoolers) available. They do not need to exist in the same book. I just want to exclude tons of children's novels that do not have a corresponding adult version.
Good examples could be some Shakespeare's works that have been edited specially for children, since there are also adult versions out there in book stores.
I want to compare language usages between the two versions. So, children versions that are abridged too much or more like explanation/summary text should be avoided.
I was quite surprised that it's very hard to find such resources on the Internet.
I really appreciate your help, teachers! Please drop the title and publisher of such books. The more the better!
Thank you!

Stories that I remember reading children's versions of as a kid: Beowulf, various Arabian Nights, Paul Bunyan, the Bible, various Greek and Roman myths. I think old stories and myths are probably going to be easiest to find. You can add King Arthur and Robin Hood also.