The most aggressive shake-up to schools in a generation, the law is the top education issue in a presidential race dominated by war, terrorism, jobs, taxes and credibility. The law orders schools to ensure all children achieve regardless of race, ethnicity or income.
For voters, the line dividing Bush and Kerry is subtle. The nominees diverge on how much to spend on the law and how much to tinker with it as schools try to comply.
The Republican incumbent promotes his spending record. He also says it is time to expand the law by requiring two more years of state math and reading tests in the high school grades.
Kerry say schools need much more money to meet high standards. He promises an extra $10 billion a year by erasing Bush's tax cuts on people earning more than $200,000. The Massachusetts senator talks of expanding the way student progress is measured in a law built on testing.
Both candidates have ideas all along the education spectrum, from college aid and teacher pay to high school rigor and math and science classes. Some ideas are modest; others would continue an expanding federal role in schools.
Yet all this is largely unnoticed by voters and lightly mentioned by the candidates, even though the next president will take on a backlog of school matters affecting millions of people
"People are still concerned about education, but terrorism and personal security have significantly increased in concern," said Republican pollster David Winston. "And then you've got a rough economy, made worse by 9-11. People are managing a lot more things."
The result has been a vastly different campaign than the one four years ago. In 2000, Bush was the Texas governor and made education a successful theme of his presidential bid. His focus on schools, traditionally a Democratic issue, helped mold his national image.
In office, he won bipartisan support in 2001 for No Child Left Behind, which calls for all students to reach state standards in reading and math by 2014. Parents get more school choices, but many schools face penalties if even a single subgroup of students falls short.
The law has not been a clear boon for Bush. States have balked at what they call federal intrusion. Some parents are perplexed to see their schools labeled as "needing improvement" under the law even if those same schools get stellar marks from their states.
"He got that law passed and has focused people on the problem of the achievement gap, and that is a big accomplishment," said Diane Stark Rentner, deputy director of the independent Center on Education Policy. But, she said, Bush did not follow through on his spending promises -- a point of endless dispute.
Under Bush, spending on the law's programs and on help for disabled children has grown from $24.7 billion to $35.5 billion, a 43 percent increase. Counting his current budget request, the increase during his term would be 49 percent, a number he cites while campaigning. Those figures would not be as high if Congress had not added billions to Bush's requests.
Still, to critics, Bush can fairly make the point, "How big of an increase does it have to be satisfy you guys?" said Tom Loveless, senior fellow at The Brookings Institution.
But Democrats say Bush has shortchanged the law by up to $28 billion. As a result, they say, everything from teaching to testing has suffered.
Democrats make that claim by comparing what has been spent on the law and the maximum allowed, called an authorization. But laws routinely are not funded to maximum levels.
"It's one of those frustrating fights. There's enough evidence for both sides to make a claim that's valid," said Andrew Rotherham, a former adviser to President Clinton. Rotherham now directs education policy at the Progressive Policy Institute, which is tied to centrist Democrats.
As for the law itself, Bush largely talks of staying the course. Kerry has signaled he may try to change how schools are graded.
Reading and math tests are the primary way states must judge student progress. Schools must use at least one other academic factor and may add others. The law says high schools must factor in graduation rates, an area where Kerry is promising more enforcement.
Kerry has raised the possibility of grading schools on such additional factors as teacher attendance and parental satisfaction. That was early this year. The campaign now uses broader terms, saying it is open to changes that ensure schools are fairly measured.
Polls taken in September after the Republican convention showed Bush and Kerry virtually tied on the issue of education, though Kerry has been slightly ahead on it through much of the year. The issue may make the difference for select groups such as married women with children, Catholics and Hispanics, said Winston, the GOP pollster.
Whoever wins will have other education issues waiting for him, including overdue updates of higher education and Head Start laws. Even so, said Loveless: "No Child Left Behind is still going to be the story out of Washington for the next four or five years."