This is a very gray area as the article states.
I do spiff my child who is in 7th grade and I do not truly believe it works as an incentive to do better. She does well with A's and B's but it is more of a pride issue.
My daughter responded better to positive re-enforcement and praise but the money comes in handy to purchase supplies for her one true love and competition pal, Austin, a sixteen hand, 3 year old horse.
I love Austin as well because barn kids are good kids and they stay out of trouble but that is another story.
What are your incentives for your children or relatives when it comes to getting good grades in school and does it work for you?
I appreciate your input so give it up for the vine!