THE REVIVED immigration bill will again be up for debate in the Senate this week. Amendments will be heard, compromises made. One element that needs that extra look is the way the bill would profoundly shift the priorities of U.S. immigration.

For more than half a century, the core principle of the system has been family reunification. The proposed bill would create instead a point scheme dominated by "human capital" considerations — those who have certain educational credentials and labor-market qualifications would be first in line at the golden door.

Such a change has long been advocated by some economists, such as Harvard's George Borjas, and by some in the business community. In the abstract, it seems to be a no-brainer. As a matter of immigration policy, we would recruit talent worldwide, enhancing U.S. competitiveness.

But this apparently unalloyed positive, in fact, is fraught with negative ramifications. Most important, the point system would deny us a rare chance to dramatically advance racial justice among native-born Americans.

To comprehend this, you must peer into the near future. The United States stands on the edge of a sea change in its demographic makeup. During the next 25 years, the mammoth baby boom generation, heavily white and dominating the best-rewarded positions in the labor market, will retire. Its retirement will create openings for others to move up, because the jobs boomers currently hold will not generally disappear. And because younger Americans are much more likely to be minorities than are the baby boomers, there is a real opportunity to reduce the racial cleavages that are so prominent a feature of our society.

Indeed, the potential for major change is already evident. For instance, in 2005, native-born Latinos and blacks made up 13% of those under age 40 holding the best-paid occupations (those in the top 25% of the labor market). By contrast, native-born Latinos and blacks represented only 6% among those 50 or older in the same job categories. The change would only accelerate as the baby boom generation retires.

However, the proposed immigration legislation represents an alternative means of recruitment to the top positions in the labor market. And it may be a very tempting one from the point of view of some policymakers and perhaps many U.S. taxpayers. Rather than having to invest in the often deplorable schools attended by home-grown minorities — disadvantaged African Americans and the children of immigrants from Latin America, the Caribbean and Asia — the U.S. could simply attract the cream of the talent from other countries, individuals whose educations have been paid for by their home societies.

It's true that many of these immigrants also will be nonwhite — the racial diversity at the top of American society seems certain to increase either way. But failing to exploit the impending opportunity to reduce our racial cleavages will leave a huge native population to continue to suffer from blocked opportunities.

Moreover, the chance to make major repairs to racial and ethnic inequalities doesn't come around very often. It requires special conditions — a situation that might be described as non-zero-sum upward mobility. That's what occurs when improved circumstances for many members of disadvantaged groups do not come at the cost of substantial losses of privilege for currently advantaged groups.

The last time it happened was during the decades after World War II. The opening came less from demographic change than a change in economic conditions.

Boom times resulted in the integration into the mainstream of the children and grandchildren of eastern European Jews, southern Italians and other immigrant populations. Once there was room to spare in the job market, colleges and universities, barriers against these groups could disappear without impinging the establishment.

We face a similar moment. If we choose to import a new, advantaged group rather than, in effect, promoting from within, American racial divides will almost certainly deepen. That will not show up on economic balance sheets in the same way that the recruitment of highly qualified immigrants will. But none of us should be fooled about the ultimate costs to our society of our deeply engrained racial injustices.