(CNN) Girls can't do math. Boys can't read.
These negative stereotypes are not only reinforced by teachers and parents but by a child's peers in the classroom as well, a new study finds.
"Our study may be the first to investigate how students' stereotypical beliefs about the reading ability of boys form what you might call the 'common stereotype' of a class, and how this common stereotype may affect students' reading outcomes," said co-author Jan Retelsdorf, an educational psychologist at the University of Hamburg in Germany.
"We looked at the impact in actual classrooms, instead of a lab," Retelsdorf added. "A key merit of our study is that we have this focus on real world stereotype effects."
The study, published Wednesday in the journal Child Development, found that girls benefited from their peer's positive beliefs about their greater ability to read.
Student stereotypes about the weak reading skills of boys, however, created a self-fulfilling prophecy of poor motivation and performance among the boys in the class.
"It's a cycle of sorts," said lead author Francesca Muntoni, postdoctoral research associate at the University of Hamburg. "Reading is first stereotyped as a female domain."
This causes boys to "devalue their actual reading ability," Muntoni said, "while also having less motivation to read, which in turn impairs their reading performance."
The study followed more than 1,500 students (49% girls) from 60 classrooms in Germany from 5th grade to 6th grade. In the first wave, researchers asked the students about motivation and confidence in their own reading abilities and administered a questionnaire about gender stereotypes and reading. Then their level of reading skill was tested.
A year and a half later, skill and enjoyment levels for reading were retested in the same students. Boys who believed in the reading stereotype were much less likely to feel good about their reading abilities, and were much less motivated to read.
If the classroom as a whole expressed a negative stereotype, that too impacted the boys' self-esteem, motivation and ability to read, at a rate that was even higher than individual beliefs.
"Boys in classes with a strong stereotype favoring girls in reading were less motivated to read," the study found, as well as less belief in their competence, in both grades, and "performed poorer in the reading test" in the 6th grade, the study found.
The cost of negative beliefs about the abilities of boys and girls have been studied for decades. A 2018 analysis of three studies found toddler boys are expected to look masculine and play with "boy toys," while toddler girls were expected to look like girls, play with feminine toys and be communal.
By elementary school, the study found, its seen as "desirable" for girls to like language and arts, while boys should be interested in math and science. Yet, national tests in the United States have shown for years that girls in elementary and middle school are as good at math and science as boys.
Many studies have looked at the impact of parents and preschool or elementary grade teachers on perpetuating those beliefs in children.
For example, a 2015 study found boys who had teachers with "traditional gender role attitudes" were less motivated to read in preschool and less competent in reading a year later. A 2016 study found parents of girls who had anxiety about math performance, especially mothers, have a significant impact on their adolescent girl's perception of her math ability.
These stereotypes have real world effects.
A 2019 study looked at 30 years of data from the federally funded National Assessment of Educational Progress, a national "report card" on American students, and found girls significantly outperformed boys in all grades in reading and writing ability, with the gap increasing from elementary to high school.
In the US and across many European countries, studies find more women enroll in colleges and have, on average, higher grades and have a higher rate of degree completion than men, Retelsdorf said.
What's to be done?
"That's a good question because as we know, changing stereotypes is very difficult," Retelsdorf said. "Our answer would be that the teachers and the parents who also have an effect on how students develop in reading should try to create a climate where individual development is the focus.
"Adults should try to be role models for this," he added. "Even though this is a stereotype, a father should perhaps not only play soccer with his boy, but read a book."