WASHINGTON, March 15 — Faced with growing criticism in school districts and state legislatures of the No Child Left Behind law, the Department of Education on Monday eased the way for schools to meet the law's requirement that highly qualified teachers stand at the front of every classroom.

Under new rules announced by the department at a news conference Monday, teachers in rural districts who are certified in one subject will have three years to demonstrate their competence in other subjects they are assigned to teach. Previously, schools had until the end of the 2005-2006 school year to ensure that all teachers were qualified in every subject they taught, and schools in high poverty areas were permitted to hire only new teachers who already possessed a background in the courses they would teach.

Officials also announced two other changes. One permits states to issue a broad certification for science teachers, instead of requiring teachers to demonstrate proficiency in each branch that they teach, like chemistry, biology or physics.

The other change is aimed at teachers assigned several subjects, many of whom feared they would have to return to school for training in their additional subjects, or to pass rigorous examinations to prove mastery. Under the new rules, states can create a single alternative assessment that will cover multiple subjects, instead of conducting a separate evaluation for each subject.

In announcing the changes, the secretary of education, Rod Paige, said his department was responding to reactions from state and local school officials. "The policies announced today offer common-sense solutions that will help states and districts get the best teachers in front of the most needy students as soon as possible," Dr. Paige said.

In earlier regulations and guidelines, the Bush administration had already set the bar for "highly qualified teachers," as the law promises, lower than many states. It said that beginning teachers, who had not yet obtained their credentials but were enrolled only in alternative training programs, would be considered highly qualified anyway.

Groups representing rural schools and teachers said Monday's change brought clarity to confusing rules. Michael Pons, a spokesman for the National Education Association, which represents 1.5 million schoolteachers, said it had asked for the streamlined alternative assessments back when the law was being negotiated in Congress, three years ago.

But education advocacy groups said that easing the law's requirements would do nothing to remedy the shortage of qualified teachers in rural schools and those with high poverty.

The Education Trust, a nonprofit group that advocates on behalf of poor, urban schools, criticized Monday's move as a retreat from the goals of No Child Left Behind, a law that the group helped write.

Ross Wiener, a senior analyst at the Education Trust, predicted that states would see in the announcement "an invitation to define their problems away, instead of a call to tackle them head-on." He said the relaxation of the rules "extends a pattern of disowning and diminishing the teacher quality provisions in the law, and postpones the day when public education will realize its goal of equal opportunity for all."