Sixteen years after Barbie dolls declared, "Math class is tough!" girls are proving that, at math, they are just as tough as boys.
In the largest study of its kind, girls measured up to boys in math in every grade, from second through 11th. The research was released Thursday in the journal Science.
Parents and teachers persist in thinking boys are simply better at math, said Janet Hyde, the University of Wisconsin-Madison researcher who led the study. And girls, who grew up believing it, wound up avoiding harder math classes.
"It keeps girls and women out of a lot of careers, particularly high-prestige, lucrative careers in science and technology," Hyde said.
That's changing, albeit slowly. Women are now earning 48 percent of undergraduate college degrees in math; they still lag far behind in physics and engineering.
But in primary and secondary school, girls have caught up, with researchers attributing that advance to increasing numbers of girls taking advanced math classes such as calculus.
Hyde and her colleagues looked at annual math tests required by the No Child Left Behind education law in 2002. Ten states provided enough statistical information to review test scores by gender, allowing researchers to compare the performance of more than 7 million children.
The researchers found no difference in the scores of boys versus girls -- not even in high school, where previous studies have suggested girls lagged slightly behind in math.
"Girls have now achieved gender parity in performance on standardized math tests," Hyde said.
The stereotype that boys are better at math has been fueled, at least in part, by suggestions of biological differences in the way little boys and little girls learn. This idea is hotly disputed; former Harvard president Lawrence Summers was castigated in 2005 when he questioned the "intrinsic aptitude" of women for top-level math and science.
Hyde has challenged that idea, arguing in an earlier study that in cognition and in many other behaviors, the two sexes are more similar than they are different.
Studies 20 years ago showed girls and boys did equally well on math in elementary school, but girls fell behind in high school. The gap has been narrowing.
Joy Lee, a rising senior at Thomas Jefferson High School for Science and Technology in Alexandria, Virginia, says she always felt confident about math, but remembers how it felt to walk into a science class full of boys. "Maybe I was a little bit apprehensive about being the only girl, but that didn't last for very long," said Lee, president of a school club that tries to get young girls interested in science and technology, along with engineering and math.
"I definitely do encourage other girls to pursue those interests and to not be scared to take those courses just because there are not very many girls or because they think they're not good enough to do it," Lee said.
Still, while there are fewer women in science and technology, there are more women in college. To Hyde and her colleagues, that helps explain why girls consistently score lower on the SAT: Far more girls take the test, and the group of college-bound students who take the test do not represent the population at large.
For the class of 2007, the latest figures available, boys scored an average of 533 on the math section of the SAT, compared with 499 for girls.
On the ACT, another test on which girls lag slightly, the gender gap disappeared in Colorado and Illinois once state officials required all students to take the test.
As Hyde and her colleagues looked across the test data, they found something they didn't expect: In most states they reviewed, and at most grade levels, there weren't any questions that involved complex problem-solving, the ability needed to succeed in high levels of science and math. If tests don't assess these reasoning skills, they may not be taught, putting American students at a disadvantage to students in other countries with more challenging tests, the researchers said.
That might be a glaring omission, said Stephen Camarata, a Vanderbilt University professor who has researched the issue but was not involved in the study.
"We need to know that, if our measures aren't capturing some aspect of math that's important," Camarata said. "Then we can decide whether there's an actual male or female advantage."
A panel of experts convened by the Education Department recommended that state tests be updated to emphasize critical thinking.
While some states already have fairly rigorous tests, "we can do a better job," said Kerri Briggs, the department's assistant secretary for elementary and secondary education.
"If we're going to be globally competitive, we need students who are able to do higher-level math skills," she said.
Back in 1992, Barbie stopped saying math was hard after Mattel received complaints from, among others, the American Association of University Women.
So far, while her current career choices include baby doctor and veterinarian -- and Dallas Cowboys cheerleader, too -- Barbie has not branched out into technology or engineering.