Btw, it's really nice of you to do this. Lots of people don't realize what those things even are.
My Mom never collected them for us and she thought it was silly when I wanted to try. And as a kid I never understood the importance.
I have about 50 of them collected so far. I figure if it can help make school better, then why not? It's not very hard to tear off the boxtop from the box of whatever.