The points system you use seems pretty clever. I've heard of one where they basically accumulate points and trade them in for something of value (anything from as small as a candy bar to something as large as a fancy motorcycle helmet!) at the end of each month/quarter/trimester. (I don't know if this has been mentioned in this topic because I haven't scanned through all the posts.)
-Justin
Eat. Skate. Sleep. Repeat.