If there is not an inherent attracting power in the material, then... the teacher will either attempt to surround the material with foreign attractiveness, making a bid or offering a bribe for attention by "making the lesson interesting"; or else will resort to ... low marks, threats of non-promotion, staying after school... But the attention thus gained... always remains dependent upon something external... True, reflective attention, on the other hand, always involves judging, reasoning, deliberation; it means that the child has a question of his own and is actively engaged in seeking and selecting relevant material with which to answer it.
If we are serious about life-long learning, then we have no choice on the matter. We have got to abolish grades so that we can cease with the artificial carrots and sticks that simply work to distract everyone from real learning.
I abolished grades 5 years ago, and it has liberated both my students and I from the reign of extrinsic terror that accompany the use of grades.
For more on abolishing grades, check out this page.