While prevailing conventional thought may be that Americans teenagers have been having increasing amounts of sex, the opposite has been true for the past 25 years. In that time, for a variety of reasons, fewer teenagers between the ages of 15 and 19 had sexual intercourse each year. That trend came to an end recently.

The Centers for Disease Control and Prevention (CDC) released a new report this week showing that the consistent decline in sexual activity had recently slowed among the age group. In response to the CDC’s findings the National Abstinence Education Association issued a statement linking what the CDC called a "stalled positive trajectory" to the country's move toward comprehensive sex education programs in schools.

The rates for female teenagers having sex plateaued between the 2006-2010 and 2011-2013 periods, and the rates for their males counterparts remained stuck around 2002’s levels, the report found. Those figures were troubling, the National Abstinence Education Association argued, because it "normalizes and condones teen sex so long as teens use contraception and devotes little emphasis to normalizing teen sexual delay."

However, a closer look at the CDC report showed rates of contraceptive use remained high while the teen birth rate hit another historic low last month, perhaps indicating that changes in culture and the ways in which teens learn about sex were making a difference. Both must continue for the U.S. to keep making headway in each category, experts on the topic of sexually active teenagers said.

"The progress has been so wide and so deep, we have to recognize there has been a shift in social norms," said Bill Albert, the spokesman for the National Campaign to Prevent Teen and Unplanned Pregnancy, a nonprofit based in Washington, D.C. But, he added: "In all of this good news, these historic declines in teen pregnancy and birth, we have to remember an important fact: what goes down can go back up again."

The teen birth rate has been falling since 1957, the height of the post-war Baby Boom, with a peak in 1991 when there were 61.8 births for every 1,000 adolescent females. The sheer number of teenagers having sex began decreasing around the same time. In 1988, 51 percent of teen females and 60 percent of teen males said they'd had sex. In the 2006-2010 period, the rates were 43 percent and 42 percent, respectively. For 2011-2013, they were 44 and 47 percent, a difference the CDC calls statistically insignificant. The teen birth rate is 24.2 births per 1,000 women.

Albert attributed the drop in part to current events. He said teens went through the Great Recession starting in 2007, a time of financial insecurity that made an unplanned pregnancy even less attractive to youths who saw their parents and siblings lose their jobs. MTV shows "16 and Pregnant," which started in 2009, and "Teen Mom," from 2011, gave viewers a first-person accounts of the very real repercussions of having sex at a young age.

School provided valuable lessons, too. Though states typically set their own rules for sex education, the White House switched things up on the federal level.

President Barack Obama created the Teen Pregnancy Prevention Initiative in December 2009, giving $110 million to entities that had "medically accurate and age-appropriate programs to reduce teen pregnancy." In his 2010 and 2011 budgets, Obama eliminated funds for about two-thirds of abstinence-only courses, a trend he continued in subsequent budget proposals, according to the Sexuality Information and Education Council of the United States. But at the same time, the Affordable Care Act dedicated about $250 million over five years to abstinence-only grant programs.

Abstinence-only education was found to have no impact on discouraging teens from having sex in a 2007 study authorized by Congress, and states with comprehensive curriculum had lower teen pregnancy rates than ones without in a 2011 study out of the University of Georgia.

Teenagers also began accessing reliable information about sex on the Internet, said Dayna Henry, an assistant professor in kinesiology and health education at Southern Illinois University in Edwardsville. "Back in the '80s, where did you get misinformation from? Your friends and your friends' older siblings and locker room talk," she added. "Kids are more savvy about what's reliable ... they have access to it in their pocket."

In general, the more teens learned, the less sex they had. They told their friends, and it created "sort of the opposite of peer pressure," Henry said. Teens were less likely to do something when they think no one else is doing it.

Though the new CDC report didn't include the data, one from 2011 found that the top reason teens said they hadn't had sex was because it was against their religion or morals. Other popular reasons included "don't want to get pregnant" and "haven't found the right person yet."

All of these things were still true, Henry said, so the CDC numbers might have stopped dropping because that's about as low as they're going to get. Teen sexual activity rates in foreign countries such as the Netherlands, France and Germany were about 50 percent, comparable to the U.S. "I don't think we're ever going to see it go down to 10 percent or something like that," Henry added.

Still, Elissa Barr, an associate professor and program director in the department of public health at the University of North Florida in Jacksonville, said she thinks sexual activity rates could rebound in the future if people aren't careful.

Barr said the media tends to glorify sex, which can influence teenagers to try it. Gone are the days of Salt-N-Pepa and "Let's Talk About Sex," she said. Celebrities rarely use their platforms to discuss healthy habits and relationships -- Instagram and Twitter make it easy for people to publicize all the good parts of having sex without ever mentioning the bad parts. “You never see any consequences, never ‘Oh, by the way, I have chlamydia,’” Barr added.

More important to Barr is that sexual education improves. Federal and state governments have begun moving toward evidence-based programs, but Barr said no matter what method schools subscribe to, they must start sooner. About a third of teens have had sex by ninth grade, so health classes that don't start until high school are ineffective, she said. She'd also like to see trained teachers and better standards.

"There's not enough of any kind of education out there," Barr said.