While waiting to get up to bat at his baseball game the other day, Harry and some of his teammates were writing in the sand with a stick. They'd write, they'd rub out - serious conversations were going on.
Later Harry came over to us.
Harry: "I'm trying to teach my teammates something but they keep rubbing it out when I write it down."
Me: "What are you trying to teach them?"
Harry: "Four Factorial."
And surprisingly the other 6 and 7 year olds weren't interested. Maybe he should try them again once they have adding and subtracting down.