The researchers polled a random sample of nearly 2000 high-school science teachers across the US in 2007. Of the 939 who responded, 2% said they did not cover evolution at all, with the majority spending between 3 and 10 classroom hours on the subject.
However, a quarter of the teachers also reported spending at least some time teaching about creationism or intelligent design. Of these, 48% – about 12.5% of the total survey – said they taught it as a "valid, scientific alternative to Darwinian explanations for the origin of species".
Science teaching experts say they are not surprised to find such a large number of science teachers advocating creationism.
"It seems a bit high, but I am not shocked by it," says Linda Froschauer, past president of the National Science Teachers Association based in Arlington, Virginia. "We do know there's a problem out there, and this gives more credibility to the issue."
When Berkman's team asked about the teachers' personal beliefs, about the same number, 16% of the total, said they believed human beings had been created by God within the last 10,000 years.