Unsurprisingly, it works. Children get better grades when they receive immediate rewards.
It's not hard to imagine why, to paraphrase one of the article's words it is easier to just hand the kids money for getting good grades immmediately rather than expect their immature minds to have the foresight to understand that they won't see any real payoff from doing well in school with a proper education until their mid to late twenties, and for many later than that considering student loans.
There are quite a few articles/studies that can be googled on the matter, it's not a new subject by any means but figured it to be interesting conversation starter.
I'm torn, it works but wouldn't that cause kids to get used to instant gratification and never learn the benefit and discipline of long-time planning and delayed rewards? Then again, the children were shown to have learned the material faster and more comprehensively when tested because they knew there would be an immediate reward.