I am a teacher and I would love to have one of your bags. Apples are never out of style for teachers. Some of the other ideas that you might also include are sayings for education that could be put on with fabric paint, or buy material with educational pictures ( children, pencils etc. and use them, as well)
The size of the bag is perfect for toting papers home to grade each night (which have to done before I start to quilt!)
Enjoy!