Two political science professors claim a strong majority of US biology teachers either don’t advocate the theory of evolution, or flat out promote either creationism or intelligent design.

The research came from Michael Berkman and Eric Plutzer of Penn State. They looked through the results of a wider survey of 926 biology teachers in public schools who’d been picked as a representative sample. The survey included statistical questions about the time spent on particular subjects, and open-ended questions about the teachers’ views on evolution.

The pair then divided the respondents into three groups:

28% structure their classes to include evidence that evolution occurred, and use it as a unifying theme (the approach recommended by the National Research Council and National Academy of Sciences)

13% “explicitly advocate creationism or intelligent design by spending at least one hour of class time presenting it in a positive light” (which largely crosses over with the 14% of teachers who personally believe God created humans)

60% do not strongly endorse either evolution or alternative explanations

The researchers noted that those in the last category adopt one of three main approaches: only referring to evolution in molecular biology terms; telling students that personal belief doesn’t matter as long as they answer test questions correctly; and presenting a range of explanations and leaving it up to students to decide.

Although the last of those options may come across as more open-minded, Berkman and Plutzer reject the approach, arguing that it wrongly presents evolution as a matter of opinion rather than fact.

The report, published in Science magazine, comes a week after the release of a national testing program’s results shows 40% of twelfth-graders failed to reach what was deemed a “basic” level of scientific knowledge for their age.