WASHINGTON - The landmark No Child Left Behind law, which has drawn impassioned criticism from educators and parents unhappy with its stringent requirements for public schools to raise students' test scores, is being rewritten on Capitol Hill to fix what the bill's authors now acknowledge are flaws.

Lawmakers say they will not abandon the basic tenets of the legislation, which requires yearly testing of elementary and some secondary school students, and holds schools and districts accountable for poor test scores.

But after five years of complaints - followed by sit-downs in recent months with teachers, administrators, and civil rights leaders - Congress and the Bush administration are ready to change the way schools and students are rated.

They say the changes will help states and school districts identify more clearly which students need extra help, while avoiding labeling entire schools as failing because they have students who are harder to teach, such as those with learning disabilities or limited English skills.

The original authors of the bill, Senator Edward M. Kennedy and Representative George Miller, are looking at a slew of changes, including expanding the way "adequate yearly progress" is calculated, so schools that barely miss the testing thresholds are not put in the same failing category as schools with across-the-board learning problems.

Other proposals include giving schools more time to improve test scores before schools are forced to take corrective action.

"Everything's up for review," said Miller, Democrat of California and chairman of the House Education and Labor Committee. "I've always said I was the proud coauthor of No Child Left Behind. ... Now, I'm determined to be the proud author of a No Child Left Behind that works."

Kennedy, who worked closely with President Bush in writing the law, has for years said the much-reviled measure would work if the administration provided the money schools need to develop good tests and help struggling students, especially those in poorer school districts.

But the Massachusetts Democrat said in a Globe interview that he now believes the law itself must be changed as well. Many of the presidential candidates in both parties have called for changes in the law, and several - including Democratic Senators Christopher Dodd of Connecticut, Hillary Clinton of New York, and Barack Obama of Illinois - have introduced legislation.

"We still have to have the concept of accountability," said Kennedy, who chairs the Senate Committee on Health, Education, Labor, and Pensions. But "what we need to do is get away from labeling, get away from the punitive aspects, and give help and assistance to the neediest schools. We're now on a pathway to make some sense on this."

Miller and Kennedy said they hope to begin work this month on writing the revised version of No Child Left Behind. The law is up for reauthorization this year, which means Congress must vote on whether to extend it.

Miller said he was pessimistic only six weeks ago that he could rally his Democratic colleagues to extend the controversial law, but has recently convinced fellow lawmakers that the law can work well if it is rewritten to address the complaints from constituents.

The law requires yearly testing in math and reading for students in grades 3 through 8; students are also tested once in high school to gauge their academic progress. Schools can be labeled as in need of improvement - and eventually, as a failing school - if students' scores do not meet what the law calls "adequate yearly progress."

The law provides for additional help for students needing assistance, and parents can also send their children to another public school if a school is deemed unsuccessful. In extreme cases, a school can be closed for poor performance.

Educators have complained mightily about the law, saying the testing rules do not fully measure whether a student is learning. School administrators say they are being wrongly punished for lower test scores from students with learning difficulties, and some parents are unhappy with schools' decisions to curtail art and music education to focus on meeting testing thresholds in math and reading.

Funding, too, is a major complaint from both educators and congressional Democrats, who say that No Child Left Behind has never been given all the money authorized in the law by Congress. The Bush administration said that funding for elementary and secondary schools has increased each year since Bush took office, often by more than it did under President Bill Clinton - a fact Kennedy acknowledges.

But states are still not getting the money they need to develop appropriate tests and provide the extra help students need to make the test-score improvements demanded in the law, Kennedy said.

Nonetheless, complaints from teachers have been so strong that some say it is unclear whether the changes under consideration will appease educators, and some political leaders, unhappy with No Child Left Behind.

While teachers say they share the goals of providing a high-quality education to all children, regardless of race, economic background, or disability, many fear that the rules might undermine public education and send more students fleeing into private schools.

"The Bush administration was setting up the public schools to fail, and to undermine public confidence" in them, said Kevin Fleming, a teacher at Winnacunnet High School in Exeter, N.H.

At a conference late last month for the National Education Association, candidates for president slammed the law, saying the testing requirements force educators to "teach to the test" and stifle creativity in the classroom.

Further, the testing structure - which holds schools accountable for the progress of an entire class, instead of individual students - is unrealistic, said NEA president Reg Weaver. "Not all children learn at the same rate, at the same speed," Weaver said in an interview.

Dodd is author of the most sweeping package on Capitol Hill to overhaul No Child Left Behind. Dodd annoyed some of his colleagues when he introduced his proposal several years ago, when the education law was still new. He is now drawing support for some of the alterations he's seeking. They include easing certification requirements for teachers and giving schools more ways to show they are making students better at math and reading.

"Test scores obviously have value, but if it's the only thing you're doing, you're not making a coherent and substantial judgment of how an individual is doing or how a school is doing," Dodd said in an interview.

More than 30 pieces of legislation to alter No Child Left Behind have been introduced on Capitol Hill, by the NEA's count - some of them from Republicans.

Senators Judd Gregg of New Hampshire and Richard Burr of North Carolina - both Republicans - introduced legislation last week aimed at keeping the accountability and testing concepts while giving more leeway to schools. For example, the bill would give schools more time to achieve test standards among children just learning English, and treat schools with small populations of low-achieving students less harshly than those with widespread problems.

The Bush administration is also ready to make some changes in the law.

The Department of Education has launched a limited program allowing several states to use different ways of calculating a school's progress in boosting test scores.

"We shifted our national education dialogue from how much we are spending to how much children are learning," Education Secretary Margaret Spellings said in a statement. "Today, we need a new conversation about how to strengthen and improve this law."