"If there is a student sitting in this gym who has had sex, let me tell you something: I am pretty sure I know about you."
That's one thing students at George Washington High School in Charleston, W. Va. heard in April. Nearly 1,000 students, on their first day back from spring break, sat in an assembly, many in disbelief.
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The speaker was Pam Stenzel, an internationally recognized, highly paid lecturer. She speaks to more than half a million young people each year, all over the world, about sexuality and the importance of self-restraint.
An 18-year-old honor student named Katelyn Campbell was outraged by Stenzel's speech, calling it "slut shaming." She explained the phrase in an interview with "20/20" co-anchor Elizabeth Vargas.
"Slut shaming was just the word in the vernacular of GW [high school] that came to mind," she said. "I mean, it's your prerogative who you want to have sex with; it's none of my business."
Slut shaming is the modern-day scarlet letter. Usually a teenage phenomenon, and done mostly online, it's calling out and shaming a peer -- usually a girl -- for allegedly being sexually active.
Campbell couldn't believe the arrows were being shot by an adult hired to speak to her school about sex.
"The tone in her videos was really combative," Campbell said. "It just seemed like she was going out to get anyone who'd already had sex."
Campbell is the student body vice president. Her 4.8 grade point average earned her a chance to speak at graduation and a scholarship to Wellesley College.
Speaking out against Stenzel turned the popular student into a pariah, and a target of criticism herself -- in local op-ed pieces, her Facebook page and elsewhere.
"It started out with people saying, you know, 'She's a slut, she's a liar, she's doing this for attention,'" Campbell said. Others took the opposite tack, posting things like "I bet she's being abstinent, but not by choice," she said.
Charleston, W.Va., and the surrounding area are known for two extremes: the antics of hard-partying college kids on the reality show "Buckwild" and devout Christian conservatism.
"There's certainly a very religious, very pro-abstinence-only group in my community who really does believe that method is effective," Campbell said.
Couldn't Stenzel's approach help lower West Virginia's rate of teen pregnancy, which is ninth in the country?
"It very well might," Campbell said. "If you're afraid of having sex, then you probably won't. But I think there's a better, more scientific way to address sex than saying, Just don't do it."
Campbell found out Stenzel would be appearing when a teacher showed her a flyer.
"One of the key lines was that Pam Stenzel will be coming to GW to discuss God's plan for sexual purity. And GW is a public school, which is really what threw me for a loop," Campbell said.
Stenzel's visit was funded by a conservative Christian organization called Believe In West Virginia.
Campbell researched Stenzel, finding some of her speeches on YouTube. One contained a message for mothers who allow or encourage their daughters to go on the birth control pill.
"This girl is going to end up sterile or dead," Stenzel says on the video.