WASHINGTON (Reuters) - The Obama administration released new guidelines on Friday aimed at promoting diversity and reducing racial isolation in education, replacing the policy adopted in 2008 under then-President George W. Bush.

Administration officials said the new guidance makes clear that educators may consider the race of students in certain plans designed to promote diversity and may reduce racial isolation among students in elementary and secondary schools.

The new policy reflected several Supreme Court rulings in recent years, including one in 2003 that reaffirmed that racial preferences can be used in university admission decisions.

But the Supreme Court since then has become more conservative and more skeptical of such programs. The court may soon decide whether to hear a case involving the University of Texas that would reconsider the 2003 ruling and the use of race in undergraduate admissions decisions.

The guidance from the Education Department and the Justice Department was sent to as many as 4,000 colleges and universities, 15,000 school districts and some 18,000 educational institutions nationwide.

It supports voluntary efforts by schools to foster diversity and recognizes learning benefits to students when campuses and schools include students of diverse backgrounds.

"Racial isolation remains far too common in America's classrooms today and it is increasing," Education Secretary Arne Duncan said in a statement accompanying the new policy.

Studies have shown that U.S. schools have become more segregated now than at the time of the 1968 assassination of Martin Luther King Jr., the African-American civil rights leader.

Educators have told administration officials that the previous Bush administration guidelines failed to sufficiently make clear that race can be taken into account as part of efforts to achieve diversity at colleges and university.

(Reporting by James Vicini, Editing by Philip Barbara)