It’s the end of the semester, which means that 70 George Mason University students are hoping I will give them an A in their required advanced composition class. Many are mystified by how college teachers grade, and they are right that the process is more complicated than it appears. As a culture, we grade everything — from restaurants to universities. Then we argue about what those grades mean. Grades for college courses are similarly open to interpretation. Professors have their own systems of awarding marks at semester’s end, and students have long since given up trying to figure out the method behind that madness.

High schools, on the other hand, pretend that a student will receive the same grade from every teacher of 11th grade English or U.S. history. But the truth, as any parent and student knows, is that grading policies — at all levels — are quite idiosyncratic.