Motoko Rich, Amanda Cox and Matthew Bloch:

Why racial achievement gaps were so pronounced in affluent school districts is a puzzling question raised by the data. Part of the answer might be that in such communities, students and parents from wealthier families are constantly competing for ever more academic success. As parents hire tutors, enroll their children in robotics classes and push them to solve obscure math theorems, those children keep pulling away from those who can’t afford the enrichment.

“Our high-end students who are coming in are scoring off the charts,” said Jeff Nash, executive director of community relations for the Chapel Hill-Carrboro City Schools.

The school system is near the flagship campus of the University of North Carolina, and 30 percent of students in the schools qualify for free and reduced-price lunch, below the national average.

The wealthier students tend to come from families where, “let’s face it, both the parents are Ph.D.s, and that kid, no matter what happens in the school, is pressured from kindergarten to succeed,” Mr. Nash said. “So even though our minority students are outscoring minority students in other districts near us, there is still a bigger gap here because of that.”

Related: Madison’s long term, disastrous reading results.