Yes, and: Additionally, universities (and, by extension departments) want grades to approximately follow a normal distribution (and yes, you in the back, their

Yes, and: Additionally, universities (and, by extension departments) want grades to approximately follow a normal distribution (and yes, you in the back, their actions show they do actually want that, even if they say otherwise). When you start grading a problem you have some idea what a "good" solution looks like, what an "ok" solution looks like, and same for "bad" solutions... If you award points based on that, the result will be a normal-ish distribution. But your idea of a good/ok/bad solution evolves as you see more papers. There's two reasons for that: First, you can't (ahead of time) imagine all the ways that students will invent to fuck up a problem set, and find edge cases in your grading rubric that result in unfairly-high or -low scores. As you gain experience teaching, you will anticipate more of the ways, but you will never anticipate every way. Second, the TA/grader wants to be able to stack-rank the papers and have the scores be monotonic. The grader wants this because non-monotonic scoring triggers far more complaining than harsh scoring or picky scoring. When you come across papers that are worse than ones you've already recently graded, you assign even lower scores. This results in a ratcheting effect with more extreme scores as you get closer to the bottom of the pile. But, since the mean score is usually a B/B-/C+ (~75-85), and since scores are usually limited to the range 0-100, this means that papers closer to the bottom will receive statistically lower scores. Now, you could go back a re-grade ones you've already done, but: 1. The university is officially only paying you for 20hrs/week (and requires a signed end-of-semester statement attesting to the same). 2. The assigned workload of teaching and grading doesn't permit a two-pass grading scheme while keeping within 20 hours. 3. If you complain to the graduate ombudsman about the workload needing more than 20 hours, you won't have funding next semester (so you have a prisoner's dilemma among TAs who might want to grade more fairly). 4. If you're grading (say) a final exam for a frosh/soph class, you're probably in a room with 4-8 other graders late into the night. One effective way to make your coworkers hate you is to be that guy who always finishes grading his stack last, when everyone is worried about catching the last train/bus. Basically, all the incentives are aligned to make this happen.