In 2005 a U.S. Department of Education study found some single-gender classes scored higher on tests. But mostly they made no difference.

Not much has changed since then.

Sara Mead with D.C.-based Bellwether Education Partners says it's still tough to draw conclusions about how well single-gender classes work.

"Overall there's some positive findings in the research,"Mead said, "but it's very mixed and overall there's not a lot of really high-quality research."Stetson University researchers have found single-gender classes typically do better than mixed-gender classes at one Florida school.

But a University of Wisconsin researcher reviewed many studies and found no evidence that single-gender classes have any advantages.

Florida lawmakers passed a law this year which allows school districts to create single-gender classes and schools.