Family Rewards Program

I'm mildly surprised, so I'll link it here: the cash-for-kids-for-academic-performance Family Rewards Program

Changed how teenagers spent their time. For the subgroup of academically proficient teenagers, it increased the proportion of those who engaged primarily in academic activities and reduced the proportion who engaged primarily in social activities;
Increased parents’ spending on school-related ...
...substantially reduced [teenagers’] problem behavior, such as aggression and substance use;
Did not reduce teenagers’ intrinsic motivation by paying them rewards for school attendance and academic achievement.

This was for low-income families; it's not obvious that it would or wouldn't work outside that context.
In the end, I suspect, a motivation program should try to affect your sense of who you are. Hmmm.
Or then again, maybe not.