"There aren't any consequences to premature sexual activity in the media, so teens receive mixed messages," Catherine Sherwood-Laughlin of Indiana University said in a statement. "They need adults in their lives to help clear up those messages."

The Center for Disease Control and Prevention's 2007 Youth Risk Behavior Surveillance System found almost half of all high school students have had sexual intercourse. About 13 percent of high school students have ever been tested for HIV, but 89.5 percent have been taught about HIV and AIDS infection.

"Parents need to set the morals, values and expectations, as well as provide education, while the schools need to provide medically accurate information and also support abstinence as the best choice for teens," Sherwood-Laughlin said.

There is a whole new language due to text messaging and the way teens communicate with today's technology, there are new words related to sex and sexual activity that parents need to know so they can understand their teens and their friends, Sherwood-Laughlin said.

She recommends parents learn teen sex lingo at the Web sites: http://www.netlingo.com/emailsh.cfm; http://www.spyonyourkids.net/spy_on_myspace_lingo_kit.php?gclid=CL6nv-nut5QCFQWVFQod2FwSTQ; and http://www.webmd.com/parenting/guide/glossary-teen-slang.