Wow - there is so much available online now including instructional videos that I hesitate to recommend anything in print form. As well, on line instruction can be tailored to the camera being used as so many digital cameras have enough minor differences that I have it very difficult to instruct without the students already knowing their own camera. Furthermore, I've found that kids who are interested are better today at self-learning using online materials than anytime in the past.
What I've found most effective is to just get them shooting in even P mode (not auto because with P mode, you can at least turn the flash on and off). Then project the images and have them collaboratively suggest improvements both visually and technically. I'm always amazed at how much they know and how much they are willing to share.
Of course you may already be doing all this and you're just here for a book recommendation!
