A student studies legal textbooks in the law faculty at Humboldt University before the start of the winter semester in 2011 in Berlin, Germany. Getty Images

Textbooks may be teaching children the wrong lessons when it comes to gender bias. According to an investigation published online Tuesday by Unesco, sexism persists in educational materials worldwide — and must be addressed before it permanently impacts kids' attitudes, academics and choices.

"Ensuring all boys and girls go to school is only part of the battle," Manos Antoninis, the director of Unesco's global education monitoring report, told BBC News. "What they are being taught is equally, if not more, important. Persistent gender bias in textbooks is sapping girls' motivation, self-esteem and participation in school."

The agency shared the blog post Tuesday, International Women's Day, in an effort to call attention to books that stereotype women, often depicting them as cooking or holding babies. In a set of Indian math books, "men dominated activities representing commercial, occupational and marketing situations, with not a single woman depicted as an executive, engineer, shopkeeper or merchant," according to the report. In China, women in books were "lifeless and dull" compared to their male counterparts.

In some countries, textbooks simply didn't include as many females as named characters and citations. For example, in Iran in 2012, as many as 80 percent of the characters in English-as-a-foreign-language textbooks produced by the national education ministry were men.

The issue is not a new one. Unesco released a similar report last year authored by University of Virginia sociologist Rae Blumberg. "If aliens beamed onto Earth and read our school textbooks, they wouldn't have a clue about what women contribute to our society," Blumberg told NPR at the time.

It's not all bad news: A few nations have worked to improve the balance in books, among them Malawi and Sweden, according to Tuesday's post. Jordan and Palestine have also recently updated texts to showcase female politicians and activists. Meanwhile, Internet users have begun to use social media to point out books they see as biased: