A sizable minority of sex education teachers does not cover all of the basics, and many lack training to teach sex ed at all, a survey of teachers in one state suggests.
In a study of sex ed teachers at 201 Illinois schools, researchers found that one-third of teachers did not give comprehensive instruction -- defined as covering the four basic topics of abstinence, birth control, HIV/AIDS and other sexually transmitted diseases.
In addition, 30 percent said they had no special training in teaching sex education, and these teachers were less likely to teach a comprehensive course.
"For this study, we set the bar for comprehensiveness fairly low relative to what most medical and public health organizations recommend," lead researcher Dr. Stacy Tessler Lindau said in a statement, "and one out of three programs failed to clear it."
The findings suggest that doctors caring for teenagers may need to "fill gaps" in their knowledge of sexual health, according to Lindau and her colleagues at the University of Chicago.
They report the study results in the journal Obstetrics & Gynecology.
The study involved 335 sex ed teachers at Illinois middle schools and high schools. Lindau and her colleagues defined "comprehensive sex education" as courses teaching both abstinence and contraception, as well as information on HIV and other STDs.
They left out a fifth, more controversial topic often recommended by public health experts: giving students information on where to go for sexual health services, condoms and birth control.
Overall, two-thirds of teachers met this more relaxed definition of comprehensive education. In general, the most frequently covered topics were HIV and STDs, which about 96 percent of teachers said they addressed. Eighty-nine percent of teachers covered the topic of abstinence-until-marriage.
Among the least frequently taught subjects were homosexuality, abortion and information on how to use condoms or birth control properly.
"Most parents support school-based sex education and teens regard it as an important source of information," Lindau said, "yet we found that several important health topics and skills are omitted, more often than not, from most Illinois public school sex-education criteria."
When it came to discussing condoms and birth control, teachers who omitted the topic generally did so because it was not in the official curriculum or because of "school or district policy." About half of teachers also lacked confidence in their ability to teach the topic -- rating their ability as anywhere from "average" to "very poor."
"Our study provides important new data from the teachers' perspective," Dr. Melissa Gilliam, another researcher on the study, said in a statement. "It supports other recent studies showing that large numbers of teens, especially low-income and youth of color, received no instruction about birth control methods before they first had sex."