WASHINGTON - The nation's schools, under deadline to get a top teacher in every core class, have won some wiggle room in areas where the task hasn't survived a collision with local reality.

Rural teachers, science teachers and those who teach multiple subjects will get leeway in showing they are highly qualified under federal law, the Education Department said Monday.

Perhaps the biggest change will be in rural, isolated regions, where thousands of teachers will get an extra year - until spring 2007, three years from now - to show they are qualified in all their classes. New rural teachers will get three years from their hire date.

The easing of rules is the latest effort by the Bush administration to show it is trying to answer the biggest concerns about the No Child Left Behind Act without weakening the law. Critics have said for months that the law makes some teaching jobs even harder to fill.

"We listened to educators from across the country, and we learned," Education Secretary Rod Paige said. He said the new guidance will help states but also ensure that the "highest standards for qualified teachers - so imperative to student success - remain intact."

The law is at the center of Bush's domestic agenda, and his officials face a public relations challenge as more schools pop up on "needing improvement" lists, state leaders talk of federal intrusion and congressional Democrats complain of shaky federal enforcement.

All states must have highly qualified teachers in all core subjects, from math to history, by the end of the 2005-06 school year. "Highly qualified" means teachers must have a bachelor's degree, state certification and proven knowledge in their subjects.

Yet in practical terms, some schools have found the requirement exasperating, particularly for teachers who handle multiple subjects. To show they are competent in their subjects, current teachers must pass a test in each topic, hold a college degree in that field or meet a standard of expertise set by their state.

Now, rural teachers will have extra time to prove they are qualified in all their subjects, provided they are highly qualified in at least one subject and get training in the others. The change will affect an estimated one-third of school districts.

Alyson Mike, who teaches at East Valley Middle School in East Helena, Mont., said the extra year "won't make a darn bit of difference" for teachers who handle several subjects. Despite the new leeway, the law will force some teachers back to school, she said. Mike, her state's teacher of the year, said it's not even clear if she meets the law's terms.

"A lot of people I know that teach in small towns, they're making $25,000 a year if they're lucky," she said. "To go back to school to get another couple of degrees, I don't see it happening."

But Tracey Bailey, a former teacher of the year from Florida, said many teachers appreciate what the law means: They should not be assigned to classes out of their field.

"It's not fair to the teacher, it's not fair to the student, and it's not academically productive," said Bailey, who helped the department gather views from teachers nationwide.

In another change, states can allow science teachers to show they are highly qualified in the broad field of science - not necessarily in chemistry, biology, or every field of science they teach. States can decide whether to require mastery of individual science disciplines.

The third change is more procedural. Under law, states must set a standard that current teachers can meet to show they are qualified in each subject without having to take a test or get a new degree - an option, the department says, that continues to get overlooked.

The new guidance says that teachers of multiple subjects don't have to go through this state evaluation process for each topic they teach; just once is fine if states choose.

"The department has done more today to show states how they can avoid addressing teacher quality problems than help them address the substance of these problems," said Ross Wiener, policy director for The Education Trust, which advocates for poor and minority students.

The changes take effect immediately, and more are coming. The department is re-examining a testing provision that requires participation from 95 percent of students.

It's unclear how many teachers are unqualified under the law, mainly because the states' collection of that data is inconsistent, a problem the department is working to fix.

Ultimately, "highly qualified" may mean something quite different from Alabama to Wyoming, mainly because the states define quality for veteran teachers without needing federal approval.

The law also does not spell out specific penalties for states that don't get a top teacher in every core class by the deadline. Department officials say they will recognize those that make good-faith efforts, but they warn of withholding money for those that don't.