Jodi-I did find most of the books were from elementary schools, but still some great material.
LindzluvzGL-The books are for ages 5-12 in my opinion, but I didn't go through all of it. I noticed some grade level stuff specifically tailored for 3rd and 4th grade, but also younger stuff like for kinder age kids
DaisyCat-Thank you for providing us this abundance of free knowledge! Let me know if you still have more left over before you head to the dump