This fall, a public elementary school in Erie will become the first grammar school in Pennsylvania to test the theory, back in vogue this century, that boys and girls learn better if they are split up.

About 160 public schools across the country offer single-sex classes, according to the National Association for Single-Sex Public Education. That's up from four in the mid-1990s.

Provisions in the No Child Left Behind Act of 2002 have facilitated the resurgence. And the Department of Education has proposed revisions to the Title IX gender-equity law that specify that segregating by gender is legal, provided enrollment in single-sex programs is voluntary and districts provide equal opportunities for boys and girls.

McKinley Elementary School in Erie will use federal funds to launch a one-year pilot project aimed at improving test scores and narrowing the achievement gap between the sexes.

Half of the school's fifth-graders will study reading and math in single-sex classrooms. The other half will study in traditional coed classrooms, Erie Schools Superintendent Jim Barker said. Teachers in coed and single-sex rooms all will be trained to focus on the distinct needs of boys and girls that are often overlooked in blended classrooms.

William Pollack, a psychologist from Harvard Medical School who wrote "Real Boys: Rescuing Our Sons from the Myths of Boyhood," has signed on to advise teachers and evaluate outcomes. McKinley teachers also will have guidance from the Ophelia Project, a nonprofit organization in Erie that has developed a methodology for creating positive, less-aggressive learning environments for girls.

The state currently has single-gender programs for middle school and high school pupils in Philadelphia and Lancaster. After reading the latest research on gender-specific instruction, however, Barker was convinced that Erie's program should target younger children.

"Children are different from the moment they're born. By age 12, males don't like to write and females start saying they're unable to do math and science. Education should be about innovation and creativity and finding new solutions to age-old problems," he said.

McKinley Principal Malinda Bostick said she had a positive experience at the Catholic girls high school she attended. When Barker proposed the pilot project in May, she jumped at the chance to do it at McKinley, an inner-city school that serves mostly low-income minority pupils. She said parents seemed enthusiastic about it and that none had expressed concern.

"I'm not intending to set women's rights or anybody's rights back 50 years. It's voluntary," she said.

Programs such as this have stirred a debate about basic equity issues nonetheless. The 1954 Brown vs. Board of Education decision outlawed segregation of any sort in schools.

Title IX education amendments of 1972 outlawed preferential or disparate treatment. No Child Left Behind loosened the rules, encouraging schools to try such innovative programs as single-sex classrooms and other reforms.

The American Association of University Women objects because schools cannot guarantee children will get the same opportunities, said Lisa Maatz, director of public policy and government relations for the group.

"The proposal to 'try out' single-sex environments was very much a red herring in trying to divert attention from the [No Child Left Behind] legislation's horrible shortcomings," particularly underfunded mandates for school reform, she said. "We know what measures work in improving student performance -- smaller class size, proper teacher training, adequate resources and greater parental involvement."

Students in same-sex classes have become "test subjects for experimentation," Maatz said.

"I do not believe I'm going to damage children by trying this," Bostick said. "There would be no polio vaccine had we not experimented on children."