In a terrific opinion piece that was prominently featured in the Sunday New York Times, Sean Reardon of Stanford University wrote that the gap between the children of the rich and the children of the poor has grown by 40% in the past 30 years.

Reardon puts to rest virtually every reformer myth: schools don’t cause inequality; schools don’t cure inequality: the achievement gap(s) begin before the first day of school. Stop blaming schools for conditions beyond their control. Poverty matters.

Reardon writes : “We are still talking about this despite decades of clucking about the crisis in American education and wave after wave of school reform.Whatever we’ve been doing in our schools, it hasn’t reduced educational inequality between children from upper- and lower-income families.”

What have we been doing for the past 30 years? Relying on standards and testing to close the gaps. It hasn’t worked.

Are schools to blame for the growing gap? Reardon says no: “It may seem counterintuitive, but schools don’t seem to produce much of the disparity in test scores between high- and low-income students. We know this because children from rich and poor families score very differently on school readiness tests when they enter kindergarten, and this gap grows by less than 10 percent between kindergarten and high school.”

If the schools are not to blame, what is: Reardon says that growing income inequality is an important cause of the growing education gap.

But that’s not all. Rich families invest their income in cognitively enriching activities: “It’s not clear what we should do about all this. Partly that’s because much of our public conversation about education is focused on the wrong culprits: we blame failing schools and the behavior of the poor for trends that are really the result of deepening income inequality and the behavior of the rich.”

What can we do? Reardon says, parent education, early intervention, support for children before the GPS grow wide: “The more we do to ensure that all children have similar cognitively stimulating early childhood experiences, the less we will have to worry about failing schools. This in turn will enable us to let our schools focus on teaching the skills — how to solve complex problems, how to think critically and how to collaborate — essential to a growing economy and a lively democracy.”