Because the grading system _encourages_ students who already know the material, and _discourages_ students who don’t know the material. If someone is discourag

Because the grading system _encourages_ students who already know the material, and _discourages_ students who don’t know the material. If someone is discouraged from a subject, they are less likely to put in the effort to succeed in the subject. This creates a self-perpetuating cycle, which ideally education would fix. Similarly, this sets students up for a false idea of their “good subjects”, when instead those are familiar subjects. A student who could be a polymath gets discouraged from pursuing multiple subjects because they’re already far ahead of the game in math, so they pigeon-hole themselves to the subject where they receive positive reinforcement. Essentially, grades as a feedback system are less than ideal, and we can do better.