Attention, students: What you learn in sex-ed class could be changing any day, if it hasn't already.

Since he's been in office, President Bush has stepped up funding to abstinence-only sexual education programs in an attempt to reduce teen pregnancy and prevent the spread of HIV/ AIDS.

Despite drawing a hailstorm of criticism from organizations ranging from the American Civil Liberties Union to the American Medical Association, federal funding for these programs has steadily increased over the past decade to nearly $1 billion.

So just what makes this form of sex ed so controversial?

Abstinence-only education instructs students that not having sex is the only way to avoid sexually transmitted diseases, unwanted pregnancies and associated health issues. It teaches teens to resist sexual advances while it reinforces the importance of marriage and cautions that sexual activity outside of wedlock may have dangerous consequences.

What it doesn't teach, however, is anything about contraception, condoms or safe sex -- information that's vital to preventing STDs and pregnancy should young people decide to have sex.

"We can only say that this is coming from an ideological place because it's not coming from a factual place," said Susan Yudt, the outgoing editor of Teenwire, a Web site by the Planned Parenthood Federation of America that focuses on teen sexual health. Planned Parenthood and other organizations that have spoken out against the rise of abstinence-only education contend that abstinence does have a place -- as a part of sexual health education -- but that to teach it exclusively is a dangerous practice.

"Study after study has shown that only comprehensive sex education -- which includes abstinence as well as birth control, healthy decision-making and preventing sexually transmitted infections -- and only that kind of sex education has been proven to reduce the risk of pregnancy and the risk of sexually transmitted infection," Yudt said.

But abstinence-only advocates believe their curriculum will result in large-scale, long-term benefits. "Teens who abstain from sex while in high school are less likely to be depressed, more likely to graduate from college and more likely to have happy marriages as adults," Robert Rector, senior research fellow for the conservative think tank the Heritage Foundation, said in an e-mail. "Teen abstinence is a positive investment in the future."

While the two sides of the abstinence-education debate argue, the fact remains: Teens are having sex. A 2002 study by the Department of Health and Human Services reported around 30 percent 15- to 17-year-olds have had intercourse, as have approximately 67 percent of 18- to 19-year-olds. In addition, a 2005 report from the National Center for Health Statistics indicated that slightly more than half of 15- to 19-year-olds in the U.S. have engaged in oral sex, which also poses disease risks.

Yudt says in light of the huge emphasis in funding for abstinence education, these statistics are especially troubling: "We're really putting teens' health and safety at risk by withholding the information they need to protect themselves against pregnancy and infection."

Several states, including Maine, California and Pennsylvania, have actually rejected federal funds for which they're eligible, rather than apply them to abstinence-only programs. But the curriculum's supporters aren't backing down, either: in April, Massachusetts Governor Mitt Romney announced that the state would use $1 million in federal funds to promote abstinence via an organization called Healthy Futures.

And while some critics of abstinence-only education point to health and safety concerns, others are uncomfortable with the ways such programs often blur the lines between church and state since they're frequently embraced by religious groups and churches that preach sex before marriage is immoral.

For example, Sex Respect -- "the world's leading abstinence education program," according to its Web site -- has a radio show broadcast on Catholic radio stations and a link to "A Christian Sexual Morality Guide For Teens." And some public schools host events (often sponsored by Christian group True Love Waits) at which students take chastity pledges -- "to God" -- that they'll remain pure until marriage.

Yet other critics are skeptical of misinformation that has sometimes found its way into the literature that accompanies abstinence education. A number of federally funded abstinence-only curricula have been censured in the past for presenting unsubstantiated claims and misinterpretations as facts.

In 2004, a study helmed by Democratic representative Harry A. Waxman of California posited that 11 out of 13 of the federally funded materials used in 25 states included questionable content. Among the contentious teachings cited in the study were that a 43-day-old fetus is a "thinking person," HIV can be spread through sweat and tears and condoms may fail up to 31 percent of the time in preventing the transmission of HIV during heterosexual sex.

Despite such snafus, abstinence-based education has wide support from religious groups, state and local leaders and the nation's leader -- President Bush received a big round of applause after declaring, "Abstinence for young people is the only certain way to avoid sexually transmitted diseases," at his 2004 State of the Union Address.

But Yudt warns that today's abstinence victories may cause problems down the road. "Teens aren't getting the whole picture when it comes to being sexually healthy," she said. "Teens will eventually become adults who are sexually healthy, but if they don't learn about using condoms and using birth control before they become sexually active, they are less likely to use them consistently and correctly when they do become sexually active either as teens or as adults."