> If 40% of a class genuinely does exceptional work, 20% get mislabeled as mediocre. If it's a weak year and only 5% are truly exceptional, 15% get a free ride.

Having been on the grading side of things, this essentially never happens. As soon as you have a pool large enough where it is mathematically sound to have a curve (30 people or so), you will not find a situation where 40% do excellent work.

Coursework follows Sturgeon’s law. In a class of 30, there’s maybe 3-4 people who do excellent work, and there is a rapid fall off from there.