Buying Used Elementary Textbooks at the beginning of the school year is a great way to lighten the load in your child's backpack.
I learned this a few years ago when I watched my youngest daughter struggle to ride her bike to school with a backpack full of books. I thought if we had a second set of books at home she wouldn't need to shuffle books between school and home.
So one night I copied all of the ISBN numbers from her books into Amazon.com and found ALL of them for $4 - $8 used.
Now every year at the beginning of school I buy used textbooks from Amazon for both of my kids so they have their regular set supplied by the school in their locker and another spare set at home for doing homework.