Instead, we should take a closer look. That was my reaction in 2004 after black Harvard law professor Lani Guinier and Henry Louis Gates Jr., chairman of Harvard's African-American studies department, stirred a black Harvard alumni reunion with questions about precisely where the university's new black students were coming from.

About 8 percent, or 530, of Harvard's undergraduates were black, they said, but somewhere between one-half and two-thirds of black undergraduates were "West Indian and African immigrants or their children, or to a lesser extent, children of biracial couples."

If we take a closer look, I said at the time, I bet we'll find that Harvard's not alone. With all of the ink and airwaves that have been devoted to immigration these days, black immigrants remain remarkably invisible. Yet their success has long followed the patterns of other high-achieving immigrants.

As one immigrant Jamaican friend once told me, "I'm too busy working two jobs to worry about the white man's racism."

Now comes a new study that finds a consistent pattern of Ivy League and other elite colleges and universities boosting their black student populations by enrolling large numbers of immigrants from Africa, the West Indies and Latin America.

Immigrants, who make up 13 percent of the nation's college-age black population, account for more than a quarter of black students at Ivy League and other elite universities, according to the study of 28 selective colleges and universities. The authors of the study, published recently in the American Journal of Education, included Douglas S. Massey of Princeton University and Camille Z. Charles of the University of Pennsylvania.

The proportion of immigrants was higher at private institutions, 28.8 percent, than at the public ones, where they comprised 23.1 percent of enrollment.

Are elite schools padding their racial diversity numbers with black immigrants who do not have a history of American slavery in their families? This development immediately calls into question whether affirmative action admission policies are fulfilling their original intent.

But as Walter Benn Michaels, a professor of English at the University of Illinois at Chicago, writes in his book "The Trouble With Diversity: How We Learned to Love Identity and Ignore Inequality," the original intent of affirmative action morphed back in the 1970s from reparations for slavery into the promotion of a broader virtue: "diversity." Since then, it no longer seems to matter how many of your college's black students had slavery in their families. It only matters that they are black.

That said, I don't begrudge black immigrants or any other high-achieving immigrants for their impressive achievements. I applaud them. I encourage more native-born American children, particularly my own child, to take similar advantage of this country's hard-won opportunities.

But I also think we need to revisit the meaning of "diversity." Unlike our current system of feel-good game-playing, we need to focus on the deeper question of how education can be improved and opportunities opened up to those who were left behind by the civil rights revolution.

We tend to look too often at every aspect of diversity except economic class. Yet, the dream of upward mobility is an essential part of how we Americans like to think of ourselves.