A study published in the latest edition of Evolution: Education and Outreach demonstrated "the average student...completed the Biology I course with increased confidence in their biological evolution knowledge yet with a greater number of biological evolution misconceptions and, therefore, less competency in the subject."
The study, conducted by Tony Yates and Edmund Marek, tested biology teachers and students in 32 Oklahoma public high schools via a survey the pair called "the Biological Evolution Literacy Survey." The survey was administered to the teachers first, to get a benchmark of their grasp of evolutionary theory. The survey was then administered twice to the students -- once before they took the required Biology I course, and once after they had completed it.
Yates and Marek found that prior to instruction, students possessed 4,812 misconceptions about evolutionary theory; after they completed the Biology I course, they possessed 5,072. Of the 475 students surveyed, only 216 decreased the number of misconceptions they believed, as opposed to 259 who had more of them when they finished the course than before they took it.
"There is little doubt," they argued, "that teachers may serve as sources of biological evolution-related misconceptions or, at the very least, propagators of existing misconceptions."
Despite holding more misconceptions about evolutionary theory after completing the course, students "presumed themselves to be more knowledgeable concerning biological evolutionary concepts following instruction as opposed to prior to instruction." They were more confident, then, that they understood evolutionary theory, even though they completed the course more confused about its basic tenets than they were when they began it.
This may be because "about one-fourth of Oklahoma public school life-science teachers place moderate or strong emphasis on creationism." In fact, two students scored higher initially on the Biological Evolution Literacy Survey than their respective teachers.
Yates and Marek note that the problem may not entirely be the teachers fault, as some research indicates that "the topic of evolution is too complex for high school students, most of whom still think at the concrete level, lacking the cognitive development necessary to comprehend biological evolution-related concepts fully and are therefore unable to construct solid accurate understandings of the topic."
["A photograph of Charles Darwin by Julia Margaret Cameron, from 1868" via Wikimedia]