Despite a court-ordered ban on the teaching of creationism in US schools, about one in eight high-school biology teachers still teach it as valid science, a survey reveals. And, although almost all teachers also taught evolution, those with less training in science – and especially evolutionary biology – tend to devote less class time to Darwinian principles.

US courts have repeatedly decreed that creationism and intelligent design are religion, not science, and have no place in school science classrooms. But no matter what courts and school boards decree, it is up to teachers to put the curriculum into practice.

" Ultimately, they are the ones who carry it out," says Michael Berkman, a political scientist at Pennsylvania State University in University Park.

But what teachers actually teach about evolution and creationism in their classrooms is a bit of a grey area, so Berkman and his colleagues decided to conduct the first-ever national survey on the subject.

' Not shocking'
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."

Better training
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.

Teachers who subscribed to these young-Earth creationist views, perhaps not surprisingly, spent 35% fewer hours teaching evolution than other teachers, the survey revealed.

The survey also showed that teachers who had taken more science courses themselves – and especially those who had taken a course in evolutionary biology – devoted more class time to evolution than teachers with weaker science backgrounds.

This may be because better-prepared teachers are more confident in dealing with students' questions about a sensitive subject, says Berkman, who notes that requiring all science teachers to take a course in evolutionary biology could have a big impact on the teaching of evolution in the schools.