Good piece, confirming many of my intuitions (critical and pre-) about the corrosive effects on learning of grade consciousness. Light on prescriptions, however -- don't give out grades for individual assignments, but tell students who ask what their grades would be if the semester were over already? Unhelpful.
Maybe ask students what their grades -- were we forced to produce such -- ought to be and why?
That might work. I often tell students that I don't know what their current grades are because they don't exist until the semester is over, but that they are welcome to do the math based on their work and the formula in the syllabus. They don't typically like this answer.
As a student, I'm more interested in being told what my grade COULD be and what I can do to achieve that. Of course, that is a question you really only need to ask in classes where there are such variables as final exam/presentation/portfolio.
Fair enough, though in general the student has exactly as much information about what the grade COULD be, and how best to accomplish that, as does the professor. For the reasons Kohn gives, it's much healthier to spend your time talking with the professor about your work and your ideas, and let those foolish little grades fall, like chips, where they may.