Jason Riley via Will Fitzhugh:

Mr. de Blasio is a progressive Democrat, and like many on the left he is quick to equate racial disparities with racial bias. But black and Hispanic students of previous generations were accepted to the city’s exam schools at significantly higher rates than today. In 1989, Brooklyn Tech’s student body was 51% black and Hispanic. Today, it’s less than 12%.

Stuyvesant’s enrollment history tells a similar story, according to Stanford economist Thomas Sowell, who attended the school in the 1940s while growing up in Harlem. The proportion of blacks attending Stuyvesant as far back as the 1930s approximated the proportion of blacks living in the city at the time. That began to change in the latter part of the 20th century, when the socioeconomic status of blacks was rising and segregation was decreasing. Between 1979 and 1995, the school’s black enrollment dropped to 4.8% from 12.9%, and by 2012 it had fallen to 1.2%.

“In short, over a period of 33 years, the proportion of blacks gaining admission to Stuyvesant High School fell to just under one-tenth of what it had been before,” Mr. Sowell writes in Wealth, Poverty and Politics. “None of the usual explanations of racial disparities—racism, poverty or ‘a legacy of slavery’—can explain this major retrogression over time.”

It is not systemic racism but changes in black cultural behaviors in recent decades that offer the more plausible explanation for widening racial gaps in education and other areas. Telling blacks that white prejudice or Asian overachievement or some other external factor is primarily to blame for these outcomes may help the mayor and his party politically, but we shouldn’t pretend that lowering standards helps blacks or any group advance.

Related: “The data clearly indicate that being able to read is not a requirement for graduation at (Madison) East, especially if you are black or Hispanic”