H.W.
I'm in agreement with Tracy-- this might not be the subject to bring up at the parent's group. Most schools are aware of the incongruities between home and school. (At least, when I was running my preschool, I expected certain thing such as no sweets, no media images coming into the school, knowing full well that the kids would be enjoying these things at home.) I would instead ask co-workers collect the box tops with you if need be.
My guess is that they are needing funding and trying to find some way to do it without raising tuition rates.