The complaints are reaching a crescendo as Congress moves closer to reauthorizing No Child Left Behind, the education reform law that President Bush passed with rare bipartisan support in 2001. Conservatives are wailing about federal intrusion. Teachers unions and some leading Democrats moan that the law relies too much on testing as the measure of student progress. And some parents echo each of those indictments.

There's no doubt the law has minted enemies. But Kati Haycock, president of the Education Trust, a nonpartisan group that advocates for low-income children, has it right when she says the law wasn't designed "to make people happy." It was passed because too many students in too many places were not learning enough. It wouldn't be doing its job if it left in place the practices that produced those unacceptable results. Grumbling, in education as in everything else, is the inevitable price of change.

And the evidence is that change is generating progress. The Center for Education Policy, an independent research organization, recently found that the share of students demonstrating proficiency in reading and (especially) math is up in most states since the law's passage. In most places, achievement gaps between white and minority students are narrowing. The problem, on both fronts, is that improvement is coming too slowly. The overall gains remain relatively modest. And the gaps between white and minority students, though narrowed, remain dauntingly wide in many places.

Those numbers — not the whining from teachers, the right or, yes, even parents — ought to be the beacon as Bush and Congress reconsider the law. Washington shouldn't try to silence the complainers but to sharpen the law's focus on helping schools and students most in need. In some cases, such an emphasis might even mute the discontent.

Currently, the law requires every state to test every student annually in reading and math between third and eighth grade and once again in high school. Schools are required to increase annually the share of students who score at a proficient level on those tests — not only overall but in eight subgroups, such as blacks or Hispanics. If the school as a whole, or even a single group, fails to show "adequate yearly progress" for two consecutive years, the school is identified as needing improvement and confronted with an escalating series of interventions that can culminate in a state-ordered restructuring.

That system — the heart of the law — is mostly admirable. It ensures that schools focus on educating all their students. The problem is that it has produced a reverse Lake Wobegon syndrome, one in which all (or at least too many) schools are below average. Fully one in five schools that receive federal Title I education dollars are now identified as needing improvement. That trend is alienating parents and educators at basically solid schools tossed onto the "failing" pile because one or two groups underperformed. It also means states must spread their resources over so many "failing" schools that they can't concentrate on the most troubled. "They are swamped," says Bruce Reed, President Clinton's former chief domestic policy adviser. "They have too many failures to fix."

The Bush administration and leading Democrats should be able to agree on a solution: establish tiers to distinguish between schools that fall just short of their annual improvement targets and those with deep, systemic problems, and then direct most attention to the latter. "We should focus our resources on the chronic underperformers," says Education Secretary Margaret Spellings. Sen. Hillary Rodham Clinton, D-N.Y., says much the same.

Keeping the focus on the neediest schools could guide other revisions. Haycock correctly argues that the $3 billion a year the law provides for improving teacher quality should be targeted more precisely toward high-poverty schools, as the law intended, rather than spread over districtwide programs, as is now often done. Washington also should require states and districts to provide more sophisticated help to schools that persistently underperform and to ensure that students in those struggling schools can transfer to other public schools and receive after-school tutoring, as the law requires. Only a small fraction of eligible students receive those services today.

With immigration reform derailed, educational accountability offers Washington its last chance for a big bipartisan accomplishment this year. It won't be easy — conservative Republicans want to repeal the federal testing mandate, and teachers unions are pressing Democrats to dilute it by allowing schools to be judged not only by test scores but by fuzzier measures, such as teacher assessments. Such changes would amount to dismantling the foundation built since 2001. The better course is to dig deeper into the law's initial motivation and more effectively lift the millions of children still left behind every day.

Ronald Brownstein is national affairs columnist for the Los Angeles Times.