The Education Department on Tuesday announced rules that will make it easier to create single-sex classes or schools, a plan that's been expected for almost three years.

The move comes as the value of same-sex education is in doubt. Research shows mixed results, as even the department's own review says.

Yet Education Secretary Margaret Spellings said more parents deserve to have the option. The push began not with the White House, but rather with female senators of both parties.

''Research shows that some students may learn better in single-sex education environments,'' Spellings said, careful not to offer an outright endorsement.

Although new federal rules may change how U.S. schools will look in the future, Utah schools are unlikely to be affected anytime soon. Carol Lear, attorney for the Utah State Office of Education, said she is unaware of any discussions or requests regarding single-sex schools or classes in Utah.

Although charter schools provide a likely venue for such an experiment, the state charter school office has not been approached by anyone interested in creating a single-sex charter school, said Jo Schmitt, charter school board secretary.

To be published today and take effect Nov. 24, the federal rules update the enforcement of Title IX, the landmark anti-discrimination law. The current language has stood since 1975.

Until now, single-sex classes have been allowed in only limited cases, such as gym classes and sex education classes.

The new rules will allow same-sex education anytime schools think it will improve students' achievement, expand the diversity of courses, or meet kids' individual needs.

Enrollment must be voluntary. And any children excluded from the class must get a ''substantially equal'' coed class in the same subject, if not a separate single-sex class.

Districts can also offer an entire school for one gender without doing the same for the other gender, as long as there is a coed school that provides substantially the same thing. Utah's Lear fears this aspect of the law could give schools license to undo the gains made in providing equal opportunity for girls in sports programs

And nationally, advocacy groups for women criticized the new rules as weakening civil rights.

''That is not a substitute for true equality,'' argued Jocelyn Samuels, vice president for education and employment at the National Women's Law Center. ''It's a very dangerous sign to schools, that they can relax their vigilance in ensuring equal educational opportunities,'' she said.

As one example, Samuels said, schools can now offer a specialized math class in physics for boys. Would the excluded girls, she wondered, get the same quality in a coed class?

Stephanie Monroe, who oversees civil rights for the Education Department, promised fair enforcement. The department will look at teacher quality, textbooks and other factors to determine whether coed classes are essentially the same quality as the single-sex classes.

About 240 public schools offer same-sex education in the United States, up from just three in 1995, according to the National Association for Single Sex Public Education.

Given new federal clarity, ''There's no question that we're going to see very dramatic growth in the next year or two,'' said Leonard Sax, the association's executive director.

He said separate classes can erode stereotypes - not reinforce them - by letting boys and girls explore their interests freely. A same-sex environment might encourage boys to play the flute, or girls to work on assembling computers, he cited as examples. Success requires involving parents and teachers, not just sticking kids in different rooms, he said.

Yet Sax also criticized the Bush administration for taking so long.

Republican Sen. Kay Bailey Hutchison of Texas and Democratic Sen. Hillary Rodham Clinton led the way in 2001, pushing single-sex education options in the No Child Left Behind law.

The department released proposed regulations in March 2004. After 31 months, an unusually long review time, the agency is releasing final rules that are substantially the same.

Monroe said the department wanted to ensure the rules follow the law and the Constitution. Still, Samuels predicted the new rules would be challenged in court. Lear concurred, saying she doesn't "see how [the new rules] could be legally defensible."

The changes affect elementary and secondary education, not colleges. The current ban on single-sex vocational education in both classes and schools at the K-12 level will remain.

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* Tribune reporter CELIA R. BAKER contributed to this story.