Many in academia have long known about how the practice of student evaluations of professors is inherently biased against female professors. Students, after all, are just as likely as the public in general to have the same ugly, if unconscious, biases about women in authority. Just as polling data continues to show that a majority of Americans think being a man automatically makes you better in the boss department, many professors worry that students just automatically rate male professors as smarter, more authoritative, and more awesome overall just because they are men. Now, a new study out North Carolina State University shows that there is good reason for that concern.

One of the problems with simply assuming that sexism drives the tendency of students to giving higher ratings to men than women is that students are evaluating professors as a whole, making it hard to separate the impact of gender from other factors, like teaching style and coursework. But North Carolina researcher Lillian MacNell, along with co-authors Dr. Adam Driscoll and Dr. Andrea Hunt, found a way to blind students to the actual gender of instructors by focusing on online course studies. The researchers took two online course instructors, one male and one female, and gave them two classes to teach. Each professor presented as his or her own gender to one class and the opposite to the other.

The results were astonishing. Students gave professors they thought were male much higher evaluations across the board than they did professors they thought were female, regardless of what gender the professors actually were. When they told students they were men, both the male and female professors got a bump in ratings. When they told the students they were women, they took a hit in ratings. Because everything else was the same about them, this difference has to be the result of gender bias.

“The difference in the promptness rating is a good example for discussion,” MacNell explains in the press release for the study. “Classwork was graded and returned to students at the same time by both instructors. But the instructor students thought was male was given a 4.35 rating out of 5. The instructor students thought was female got a 3.55 rating.” Considering that professors were rated on a five-point scale, losing an entire point on the “promptness” question just because students think you’re female is a major hit.

This particular study is small, so we shouldn’t get carried away about its results. But it certainly suggests an important avenue for future research. Students penalized the perceived female professor in all 12 categories, including in qualities that women are usually assumed to excel at, such as being caring and respectful. This comports with other studies that show that while female professors are judged somewhat less harshly if they conform more to female stereotypes, men still get bonus points for showing up male.