Standardized tests show that girls — whether elementary students or college freshmen, here or around the world — know more than boys.

Girls score better in reading, writing, math and — to a lesser degree — social studies.

Boys do only marginally better in science, but as hard-wired gender roles shift and educators increasingly pitch engineering to under-represented women, girls are catching up in that last subject where boys dominate.

Women are excelling in college, too.

Between 2009 and 2013 women ages 24 and up earned four-year degrees 64 percent faster than men. More shocking is that also in that five-year window, the number of professional and graduate degree-holders grew 120 percent faster for women, according to U.S. Census Bureau data.

Despite their academic achievement, women still earn less than men regardless of college. Though the wage gap is shrinking, the longer a woman spends in college, the more likely a man with the same education level will be paid even more than her.

Several theories attempt to explain why boys and girls have markedly different educational outcomes:

• Because the academic gap exists across ages, societies and races, researchers suggest that intellectual maturity and normal child development favor females. The gap is widest at the middle-school level.

• Physiology plays a role. Adolescence can disrupt education as boys and girls develop. The age of puberty is when teachers begin to see the differences.

• Behavior is big. Boys are 2½ times more likely to be suspended and nearly three times more likely to be expelled. They also drop out of school more often.

• Girls might think differently. Educators say they are less oppositional and are deeper thinkers.

• Society could be to blame. Boys are encouraged to be aggressive, which would explain the defiant behavior and the dominance in high-paying corporate positions. Stereotypical gender roles drive boys to competitive sports and girls to reading and writing — two subjects in which they dominate boys.

What society expects of men and women influences, to some degree, how teachers instruct and how boys or girls learn.

"I think our society is so confrontational for males. It's such a hyperaggressive society," said Walter Jacoby, who coaches tennis to high school boys in Cuyahoga Falls and girls at Our Lady of the Elms, an all-girls private school in Akron, Ohio.

Jacoby first taught inner-city boys and girls at Innes Middle School in the late 1990s. In the past 15 years of teaching social studies to girls at the Elms, his thoughts about gender and education have evolved.

"Men get prized for their aggressiveness now, especially when I was in the inner city. It was bigger, stronger, faster. And the fact is that the only route out for so many of these kids is athletics. That's what they're pushed to."

Jennifer Milam, elementary principal at the Elms, said that teachers often aren't even aware how much society shapes their outlook.

"To some degree, it is so ingrained in us that girls are interested in this and boys are interested in this, that it is subconscious on the teacher," she said.

But as the mother of a boy and a girl, she realizes that the implications can be ominous.

"If my son decides he wants to be a ballet dancer, he's going to catch a much different response from the people around him. And he's only in first grade," she said. "In our world today, I think it is much more acceptable for young women to be confident and strong than it is for men to be kind and nurturing. We still have that same old stereotypical vantage point."