I tried the exact thing you’re talking about, with very similar dollar values you’ve put forth.
The results were mixed.
One child did have a noticeable improvement for a half-year to a year, then things went back to As and Bs, just like they had been before. Very smart kid who just put forth the effort in subjects that were appealing, basically.
The other child was intrigued by the idea and I saw a blip upward for a little while, but that was about it….returned to Bs and Cs.
My take on it: a grading interval is way too long to be much of an incentive…the carrot is too far out there for most kids. I think your purpose would be better served if you gave $$ for every test they took. Of course, this would mean working closely with the teacher to determine what tests would be given and to ensure tests weren’t “manufactured” to pad their wallet, but I think this arrangement would work better. And if they do well on all the individual tests, the better grade in the entire course will follow.
