> There are 24,000 high schools in the US (not even considering international students) with wildly varying grading standards. You have one applicant from Podun

> There are 24,000 high schools in the US (not even considering international students) with wildly varying grading standards. You have one applicant from Podunk City High School, valedictorian with a 4.0. Is that ... good? How does it compare to the thousands of other kids with 4.0s you have applying? Some other places in the world admit based on the Z-score for each subject, with the average and standard deviation being specific to each school. While the university might not know how one would compare to other students based on an equivalent test, they'd at least know that a particular student is in the top decile for their school in a given subject.