A new study claims negative gender stereotypes can help explain why boys lag behind girls in the classroom.

The old saying goes that boys are made of “snips and snails and puppy dog tails,” and low and behold, those qualities don’t make for good test-takers. The “sugar, spice, and everything nice” girls are made of means they behave well and do better in school, right?

New research says common gender-based stereotypes like these give girls an academic advantage over boys.

Researchers from the University of Kent sought to answer this fundamental question: why are boys underachieving at school? The short answer, they say, is that the negative stereotypes about boys’ achievement may hinder their academic potential.

A self-fulfilling prophecy is an expectation that influences a person’s behavior to the point that the expectation becomes reality. For example, if someone tells you you’re not going to do well on a test, there’s a good chance you won’t.

The British researchers found that this kind of self-fulfilling prophecy hinders the academic achievement of boys, at least among primarily white schoolchildren in the U.K.

“People’s performance suffers when they think others may see them through the lens of negative expectations for specific racial, class, and other social stereotypes—such as those related to gender—and so expect them to do poorly,” Bonny L. Hartley, a PhD student at the University of Kent who led the study, said in a press release. “This effect, known as stereotype threat, grants stereotypes a self-fulfilling power.”

The researchers focused on the role of gender stereotypes in the classroom and on how they affect the prospects of young children.

In three separate studies, researchers found that children often think boys are academically inferior to girls, and that adults share this same belief.

In the first study, researchers examined gender stereotypes related to conduct, ability, and motivation. They quizzed 238 children ages four to 10 about what kinds of statements they associated with a silhouetted picture of a boy or girl. Overall, children attached positive statements (“This child really wants to learn and do well at school”) to girls, while boys were viewed more negatively.

This suggests, researchers said, that children felt girls were better behaved, performed better, and understood their schoolwork better than boys. This surprised the researchers, considering that the white boys “are members of a non-stigmatized, high-status gender group that is substantially advantaged in society.”

This self-fulfilling prophecy of male inferiority affected the boys’ performance when researchers gave them academic tests.

In another study, students ages seven and eight were told prior to a test that boys did worse than girls on tests. This caused the boys’ scores in reading, writing, and math to drop. When tested after being told that boys and girls perform at the same level, the boys’ test scores improved and the girls’ performances were not affected.

The research team’s findings were published in the journal Child Development.

Teachers, parents, and children shouldn’t be told that one gender is superior to the other, especially in light of evidence that these stereotypes are damaging.

Stereotyping children as young as four serves no purpose and should cease, no matter if it’s based on gender, race, or another superficial factor that has no bearing on a person’s character or ability to succeed.

“In many countries, boys lag behind girls at school,” Hartley said. “These studies suggest that negative academic stereotypes about boys are acquired in children’s earliest years of primary education and have self-fulfilling consequences. They also suggest that it is possible to improve boys’ performance, and so close the gender gap, by conveying egalitarian messages and refraining from such practices as dividing classes by gender.”