New York, Dec 14 (IANS): Fewer than half of high schools and only a fifth of middle schools in the US teach all the topics recommended as essential for sexual health education, a new survey shows.

The recently released findings are based on US Centers for Disease Control and Prevention's (CDC's) 2014 school health profiles -- surveys that ask schools across the country whether they teach essential topics in HIV, sexually transmitted diseases (STDs), pregnancy prevention, and other health subjects.

"We need to do a better job of giving our young people the skills and knowledge they need to protect their own health,” said Jonathan Mermin from CDC.

"It is important to teach students about healthy relationships and how to reduce sexual risk before they start to have sex,” Mermin noted.

The topics that CDC select range from basic information on how HIV and other STDs are transmitted -- and how to prevent infection -- to critical communication and decision-making skills.

According to a CDC report, the proportion of teenagers who have ever had sex has remained unchanged (at about 47 percent) for a decade - 15 percent of teenagers in 2013 said they had had four or more sexual partners, the same number as in 2003.

"Lack of effective sex education can have very real, very serious health consequences,” Stephanie Zaza, director of CDC’s division of adolescent and school health, said.

"Young people who have multiple sex partners, do not use condoms, and use drugs or alcohol before sex are at higher risk for HIV and other sexually transmitted infections. School-based sex education is a critical opportunity to provide the skills and information they need to protect themselves,” Zaza said.