You're misreading the text. The K-6 references are about banning teaching of sexual orientation and gender identity. The parts about "Age appropriate books" are

You're misreading the text. The K-6 references are about banning teaching of sexual orientation and gender identity. The parts about "Age appropriate books" are specifically for all school levels K-12 (scroll down in the statute to find the twelfth grade reference). I guarantee you that these books were not on the shelves in K-6 libraries.