Interesting and troubling research on rising income inequality in recent decades, which has led to rising educational inequality:

Duncan and Murnane make the case that the ability of the affluent to invest in their children has contributed to the "growth in the income-based gaps in children's reading and mathematics achievement" which, in turn, has "contributed to a growing gap in the rate of college completion." The two authors also document the growing disparity of parental financial investment in "child-enrichment goods and services." In 1972-73

high-income families spent about $2,850 more per year per child on child enrichment than low-income families did. By the 2005–2006 school year, this gap had nearly tripled, to $8,000

in inflation-adjusted dollars. While several of the Russell Sage authors cite the success of a few specialized education programs in raising the academic achievement levels of low-income students, the report suggests that given unequal circumstances at birth, over which children have no control, traditional schooling may be aggravating pre-existing disadvantage.

Two report authors, Isabel Sawhill and Richard Reeves, both of Brookings, found that:

among children born of normal birth weight to married mothers who were not poor and had at least a high school education at the time of their child's birth (advantaged-at-birth), 66 percent can be expected to be ready to start kindergarten, versus only 46 percent otherwise. This gap never narrows.

Citing the work of Sean Reardon of Stanford, Duncan and Murnane point to a substantial increase in the test score gap between low and high income students taking the SAT:

In the late 1960s, test scores in reading of low-income children lagged behind those of their better-off peers by four-fifths of a standard deviation — about 80 points on an SAT-type test. Forty years later, this gap was 50 percent larger, amounting to nearly 125 SAT-type points.

Bradbury and Triest, the Boston Federal Reserve economists, follow up by drawing attention to the inexorable disadvantages accruing to already disadvantaged kids:

A 40 percentage-point gap in college enrollment of students born in the early 1960s between poorest-quartile and richest-quartile students expanded to a 51 point gap for the later cohort; similarly, the earlier cohort's 31 point gap in college completion between rich and poor grew to a 45 point gap for the later cohort.

Bradbury and Triest put forward a bleak assessment of the options available to young people born into the poorest families, even children who possess considerable native gifts:

A key question is whether primary schools, once children come under their care, level the playing field and reduce these disparities. Most research findings suggest that they do not.

Not only do "children of affluent parents graduate from college at substantially higher rates than children of low-income parents," according to Bradbury and Triest, "the gap persists even when controlling for ability in the form of test scores."

They cite data showing that

a child's earnings in adulthood reflect parental investments in his/her human capital (education) as well as his/her endowment of earnings capacity and market luck. That endowment, in turn, is determined by the reputation and "connections" of their families, the contribution to the ability, race, and other characteristics of children from the genetic constitutions of their families, and the learning, skills, goals, and other "family commodities" acquired through belonging to a particular family culture.

Four key factors or mechanisms of intergenerational earnings persistence "that are related to family incomes and that have a return" in the labor market play an outsize role in determining the fate of American children, according to studies cited by Bradbury and Triest: "noncognitive skills, cognitive ability, early labor market experiences, and educational attainment."