In standardized education the primary purpose of an exam is to measure how much a student is “worth.” This is wrong. The primary purpose of an exam should be to determine what the student knows.

What is it that people do with exam grades? They use them to compare students against each other, as a way to determine which students are “better” than other students. A grade serves much the same function as a price in a marketplace—it abstracts away all of the details until you have a single number that you can use to compare unlike things. Grades are one of the primary metrics for determining whether a student will be admitted to a university, admitted to a doctoral program, or offered an internship or job. The primary purpose of exam grades is therefore to determine which students are “better” or “worse” than others, because that is how people use grades.

I think it’s wrong to abstract away all information about a student’s knowledge until all that is left is a single, crude numeric measure. When a teacher (or a student) sees a grade, it is an extremely imprecise error signal.

The purpose of teaching is learning, and learning is better served by a precise error signal, one which gives the student and the teacher feedback about what the student does know and what the student doesn’t know. Exams and grading must be structured so that they are a measure of knowledge and knowledge gaps. Until then, exams will be a measure of “worth,” and students who do poorly on exams will view themselves as being unworthy or less valuable when they instead should view themselves as just not knowing something yet.