Pippa Biddle always said she would never attend an all-girls school. She reluctantly agreed to visit Miss Porter’s, an all-girls boarding school in Farmington, Connecticut, as a favor to her mom. But after spending one night at her mom’s former high school, she decided to apply. “Until you experience a single-sex classroom, it is hard to understand how beneficial it is,” Biddle, who’s 21 now, tells me. “I could wake up five minutes before class, pull on clothes, and feel just as beautiful as I would have with full hair and makeup. The value was put on who we were, not what we look like.”

Despite personal testimony from young people like Biddle, opponents of single-sex education argue that separating children by gender is not only sexist, it also leads to harmful gender stereotyping. They also state that the existing science does not show that same-sex education has tangible benefits and that public funding should not be used to support segregating students by gender. These opponents of separate-sex education have a new study to back up their claims: Last month a meta-analysis of 184 studies covering 1.6 million students from 21 countries indicated that any purported benefits to single-sex education over coeducation, when looking at well-designed, controlled studies, are nonexistent to minimal.

Yet interest in the potential promise of single-sex schooling continues to grow. More than 500 American public schools in the 2011-2012 academic year offered their students single-sex opportunities ranging from separate classes for physical education to entire school days with all activities being either all-boy or all-girl. They include schools like Girls Preparatory Academy at Ferrell Middle Magnet School and its counterpart, Boys Preparatory Academy at Franklin Middle Magnet School, in Tampa, Florida, and G. James Gholson Middle School, near Washington, D.C., which offers single-gender classes in courses such as math and science.