When it comes to gender equality at business schools, it’s not just about the percentage of female students. What exactly those students are learning is also vitally important.

A new analysis published in Harvard Business Review finds that, from 2009 to 2015, just eight of 74 best-selling case studies—the primary teaching tool in many schools—featured a female protagonist. A full 62 had male protagonists, while four had no clear central character.

Drill down, and the numbers get even worse. Of the 21 cases published in the last two years, just a single one included a female lead. Altogether, the 21 cases from 2014 and 2015 feature 222 characters, only 21 of whom are women.

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Business schools have come under increasing pressure to become more female-friendly. While enrollment has been a big focus—women now make up an average 36% of full-time students at 36 of the big b-schools—the institutions are also beginning to pay more attention to the way gender plays out in their curriculums. Indeed, at a White House event last summer 45 schools committed to a best practices document vowing to include more women in teaching materials like cases studies, according to HBR. Clearly, they still have a long way to go.

Leadership coach and study author Lesley Symons offers three suggestions:

Start in the classroom. Professors must address gender issues in cases head-on, talking openly with students about how women are portrayed—are they shown as business leaders? As customers? Do they talk to other women about business? Since professors often teach their own cases, schools should encourage their faculty to write cases that include female protagonists.

Get clearing houses involved. Case clearing houses, which distribute the materials to business schools, should begin gathering data on how many of their cases feature women and make that information easily accessible on their websites. They might also create special awards for female-driven cases.

Pressure from employers. Companies that hire from business schools should ask questions about teaching materials and how gender is discussed in classes.