SAN JOSE, Calif. - A new study puts to rest one of the most widespread myths about boys' and girls' aptitude in math. After analyzing 7 million test scores, researchers found no difference.

The findings demonstrate great strides since the 1970s when major studies showed pronounced differences in the scores of males and females. By the 1980s, younger students were matched, but girls fell behind when they hit adolescence.

Study authors at the University of California-Berkeley and University of Wisconsin-Madison offer several theories behind the improvements, including changes in educational approaches and career expectations.

"Stereotypes are very, very resistant to change, but as a scientist I have to challenge them with data," said Wisconsin's Janet S. Hyde, lead investigator of the study, published in today's

issue of the journal Science.

Using vast data generated by the No Child Left Behind legislation, which mandates annual testing of youth from elementary school through high school, the new study concludes that the gender gap has vanished among students of all ages.

Among math whizzes, there remain sex differences.

But they don't add up to anything definitive. For instance, there are more white boys than girls with scores in the 99th percentile. But among Asian-Americans, it's reversed: Girls outperform boys. (Reliable data was not available for Hispanics, blacks and American Indians.)

The concept of male supremacy in math became established among many educators and psychologists in the 1970s with the publication of the book "The Psychology of Sex Differences," written by Stanford emeritus professor Eleanor Maccoby and University of Southern California emeritus professor Carol Nagy Jacklin.

The notion has driven generations of girls away from advanced high school math, legitimizing a pernicious sexual stereotype, feminist scholars have asserted.

But attitudes - and aptitudes - have been changing.

In 2005, after former Harvard President Lawrence Summers suggested that women may be biologically unsuited to succeed at math, he was ultimately subtracted from the top post.

"Going back to my mother's generation, for example, women were commonly encouraged to avoid math courses," said Suzanne Antink, a calculus teacher at Palo Alto High in Palo Alto, Calif. "I experienced a male math teacher my senior year with the same idea ... from his point of view there was no reason for women to be in his class. We have come quite a way since then."

Today, roughly half Palo Alto High's calculus students are girls, and the Advanced Placement statistics course is 60 percent female.

Girls are doing better because they are taking more advanced courses in high school, according to the research team. After tackling subjects like multi-variable algebra, analysis and calculus, girls are scoring higher on tests.

"Now that enrollment in advanced math courses is equalized in high school, we don't see gender differences in performance on state tests," said co-author Marcia Linn, a UC-Berkeley professor of education.