For about three years I have had my undergraduate TAs do a lot of my grading. I can write more one day on what I ask of them and why I like them. Over that time period, I have taken samples of about 5% of the things that they grade, and quietly grade them myself typically before the TAs get their hands on them. In every single one of my courses I have found that my student TAs are statistically significantly more likely to grade tougher than I do. The effect isn’t huge, about a 2 to 4 percentage point difference (i.e. 1 point on a 25 point exam), but it is clearly there.
And I am a tough grader (or so I think).
What to make of this? Well, for all of this hand-wringing about grade inflation and the decline of merit and standards in the academy, it seems to me that my students do not wish to see their grades inflated. Maybe of course this is the self-interest of the TAs speaking – after all, they are probably those who most suffer from the problems of grade inflation. If there is grade inflation, it is the formal and informal pressure put on me about what to do with these grades. My deepest sentiments believe that an average student should be given a C. But that is so far below what the average student gets even in a tough grading department that it would be a massive disservice to my students to keep to that metric. So, in some sense, the rigidity with which my students grade each other is not an issue since it is the variation/consistency in the grading that I care most about.
Without an exegesis on grading and the problem of inflation, these experiences of mine seem to indicate to me that students would prefer if the other equilibrium in this game theoretic problem were reached. It’s just that such an equilibrium is not likely to be stable.
Might I suggest that your TAs work hard for their grades, and are surprised at how little effort and comprehension passes for a decent grade?
From my experience, “good students” tend to grade harder then their professors.