We will be reusing these bags again this year. Despite being thrown around, drug through the dirt and across the gravel parking lot, and various other mistreatments, they are still in excellent shape.
I did not do a whole lot of research for you on "green" backpacks because there are just so many out there to choose from. There are some things you should look for though.
1. First and foremost - STAY AWAY FROM VINYL BACKPACKS! Those characters are cute, but they are also made from highly toxic Polyvinyl Chloride (PVC). These backpacks also tend to be low quality and are almost always made in China.
2. Check out your local thrift stores - great backpacks can frequently be found for very cheap. Plus, you are reusing, which is one of the 3 R's of green living!
3. Look at the materials used in the backpack - shoot for organic cotton or other sustainable fibers. Hemp and bamboo are the first that come to mind. There are also backpacks out there made from recycled nylon or other recycled materials. Paige and Summer's backpacks are from Keen's Harvest Collection, which are made from 100% recycled rice bags and repurposed excess factory materials from their shoe production.
4. If possible, as in all things, choose MADE IN THE USA!