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.

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."