U.S. eases limits on single-sex schools School districts across the nation this fall will have unprecedented freedom to open up all-girls' or all-boys' schools and classes under sweeping new regulations announced on Tuesday by U.S. Education Secretary Margaret Spellings. The shift is the biggest in 31 years and for the first time allows schools to separate students by gender if they believe it helps — a standard that is under debate in the existing research. Participation in such programs would be voluntary, but schools choosing to separate a class for one sex wouldn't have to provide an equivalent class for the other sex. They'd simply have to offer a "substantially equal" coed class in the same subject. The rules, which take effect Nov. 24, also clarify rules on creating entire single-sex public schools. Since the current rules went into effect in 1975, single-sex classes have been allowed only on a limited basis, such as in charter schools, sex education courses or gym classes involving contact sports. The Bush administration, supported by both Republican Sen. Kay Bailey Hutchison of Texas and Democratic New York Sen. Hillary Clinton, has favored loosening the rules. About 240 public schools offer same-sex coursework, up from just three in 1995, says Leonard Sax of the National Association for Single Sex Public Education. He thinks about 1 in 10 of the nation's 90,000 public schools could decide to become single-sex. Critics, such as the American Association of University Women and the American Civil Liberties Union, call the changes troublesome. Emily Martin of the ACLU Women's Rights Project said the new regulations "represent a through-the-looking-glass interpretation" of the federal Title IX law, which prohibits excluding students from school programs on the basis of sex. She noted that schools could now "separate girls and boys for virtually any reason they can dream up — including outdated and dangerous gender stereotypes." Spellings said research shows that "some students may learn better" in single-sex environments, but other administration officials on Tuesday admitted that the best research offers only tepid support. A 2005 analysis of current research, cited on the department's website, noted that "any positive effects" of single-sex schooling on long-term academic achievement "are not readily apparent." The analysis found no differences on college test scores, graduation rates or graduate school attendance and bemoaned "the lack of high-quality research on these important criteria." And it found no research on how single-sex schooling affects critical factors such as teen pregnancy rates, differential treatment by teachers, parental satisfaction and school bullying. Speaking to reporters on Tuesday, Stephanie Monroe, who heads the department's civil rights office, minimized the research, saying that as a parent she'd want all options available to her child. "The department believes that this is an option that should be made available," she said. Contributing: The Associated Press Enlarge By James Gregg, Arizona Daily Star via AP Eighth-grade classmates, from left, Anamaria Alvarez, Hafsah Khan, Nubia Amaya and Karen Perez, raise their hands to answer a pre-algebra question at Sahuarita Middle School in Tucson, where math classes are segregated by gender.