What books kids bring to school is one thing. What gets taught and assessed is another. You make a good point regarding some of the more bizarre sexually explicit and violent specific stories - but basic concepts written in the Bible - New Testament (along with basic ideas/concepts written in the Muslim Quran, Hindu Shreemad Bhagavad Gita - Upanishads - and Veda, Buddhist Tripitakas, and the Jewish  Torah and Talmud) are totally appropriate for elementary kids - especially when those ideas permeate so much of our culture like it or not.