Once upon a time, colleges selected applicants on the basis of academic merit. Then came affirmative action, which introduced racial and ethnic factors into the mix. And the rest is history.

Right? Wrong. Race and ethnicity have always mattered in college admissions. But they mattered in different ways at different times.

That was the key insight of Harold S. Wechsler, who died last Thursday. Wechsler’s first and best-known book, The Qualified Student (1977), shattered any myths we might have had about a golden age of American meritocracy. Going back to the early 20th century, American colleges changed the rules of the game whenever academic standards started to generate the "wrong" kind of applicant.

And then there was the question of how — and whether — colleges would integrate the students whom they did admit. That was Wechsler’s other big concern, and it wasn’t just a scholarly one: It was deeply personal. More than anyone I have ever met, Harold Wechsler put the needs of his students first. And those needs would inevitably differ, depending on where the students came from and how they got in.

Consider Harvard, which adopted the College Entrance Examination Board as its key basis for admission in 1905. Worried that it was enrolling too many mediocre young men from elite prep schools, Harvard decided that a standardized test would help attract and enroll a higher-caliber student.

But there was one big problem: Too many of those higher-caliber students turned out to be Jews. By 1908, the percentage of Jews in Harvard’s freshman class jumped from almost zero to 7 percent; a decade later, it had risen to 20 percent. That was too much for A. Lawrence Lowell, Harvard’s president, who worried that Jews’ alleged "clannishness" would drive away Anglo-Saxon applicants — and, eventually, even qualified Jewish ones. ...