Childhood pay for grades is related to college grade point averages.

@article{Flora2004ChildhoodPF,
  title={Childhood pay for grades is related to college grade point averages.},
  author={Stephen Ray Flora and Stacy Suzanne Poponak},
  journal={Psychological reports},
  year={2004},
  volume={94 1},
  pages={66}
}
In a sample of 87 college students from four junior level courses, being paid for earning good grades in childhood was related to higher college GPAs relative to students who were not paid for good grades in childhood.