Also check out freecycle.org and post that you are a new teacher and need children's books. Many people will clean out their closets and donate them to you. I also offered my kids an incentive for them to bring in their old books (with parent permission of course). I operated a swap shop in a sense. We have a classroom economy and the kids earn money through multiple ways. Kids brought in their old books and I paid $25 in class cash for each book. I collected over 200 books that way!!!