There's a good deal of confusion about what it means to close the achievement gap in education. There's the question of what is being measured. Is it the difference in average standardized test scores? Is it grade-point averages? Is it dropout rates? Is it graduation rates? And there's the question of who is being measured. Is it students from wealthy families and those from low-income families? Is it black students and white students? Is it male students and female students? Different scholars use different definitions.

Further complicating the matter, the rhetoric suggests that closing the achievement gap is always good thing (indeed, it's a major goal if not the major goal in U.S. education reform). But logic tells us that's not necessarily the case. For instance, you could close the achievement gap and have all students performing at lower levels than ever. Or you could close the achievement gap by having low-achieving students perform a little better and high-achieving students perform much worse.

This is the concern raised by Tom Loveless in his new report, " High-Achieving Students in the Era of No Child Left Behind," issued by the Thomas B. Fordham Institute, a nonprofit organization that works with schools in Ohio and advocates for school choice for families. Loveless is troubled to find that while the scores of low-income students did rise significantly, the scores of high-income students barely budged, according to data from the National Assessment of Educational Progress:

"Gaps are narrowing because the gains of low-achieving students are outstripping those of high achievers by a factor of two or three to one," writes Loveless. "The nation has a strong interest in developing the talents of its best students to their fullest to foster the kind of growth at the top end of the achievement distribution that has been occurring at the bottom end. International comparisons of top students around the world invariably show American high-achievers falling short."

Another recent report that analyzes NAEP data, this one from the Center on Education Policy, also found that minorities and the poor are making the greatest gains on national standardized tests, but the center had a different conclusion—namely, that this is good news. "The nation has sought to raise test scores and to narrow the achievement gap," writes Jack Jennings, president and chief executive officer of CEP. "These results show that we are making progress, although much more work needs to be done."

Perhaps both analyses are correct: The progress of disadvantaged students is good news, but it's not to the benefit of students who are already performing at a high level. Every policy yields a winner and a loser, and schools are in the difficult position of having to cater to every type of student at once. If the emphasis is put on helping struggling students, high-performing students most likely will receive fewer resources.

There's certainly more that can be done to help high-performing students (like creating achievement mandates and programs for them, or tracking their progress and rewarding schools that improve both their scores and the scores of struggling students). Given the finite public resources and the huge disparities between the standardized test performance of haves and have-nots, perhaps it's fair that the emphasis is placed where it is. Of course, that logic is a bit harder to swallow at the personal level: If you had a high-performing kid, would you want her in a classroom where she is not the priority?