These examples suggest, rather frighteningly, that a group of people can engage in systematic bigotry, even when a majority of them are not actually bigots. That's not group-think, where people think and act the same way when they get together. Rather it's group-ignorance: people thinking one thing and doing another, because they are deluded about the majority's real views and then are conforming to that delusion.

Perhaps you're looking back up at the headline by this point and wondering what does all this have to do with high school?

In fact, what doesn't peer pressure conducted under a cloud of ignorance have to do with high school? To be a teenager is to be the subject of nearly universal misunderstanding. Teens appear as strangers to their own parents, as hormonal monsters on television, and as flighty naifs, with smartphones grafted to their palms, in the media. But it turns out that teens are just as hopeless at assessing themselves. A new study of high school behavior finds that young people wildly over-estimate the sex and drug life of their own classmates and even their own cliques.

Popular kids and male jocks aren't having nearly as much sex, or doing nearly as many drugs, as other high schoolers assume, said Geoff Cohen, a co-author and professor at Stanford University. "Teenagers grossly overestimate the amount of substance abuse of [pot heads] and the sex life of jocks," he said. "We knew there were stereotypes, but we were surprised by the level of caricature."

High schoolers assumed that jocks and popular kids drank more alcohol and had more sex than average students. But jocks' and popular teens' self-reported sexual behavior wasn't significantly different from the “brains” or the “others.” (The fact that kids vastly over-estimate popular men's self-reported sexual behavior is particularly interesting, because if men were going to lie about their own record, they would probably “lie up” to exaggerate their romantic successes.) The misconceptions didn’t always skew toward deviant behavior, either. Smart kids reported studying only about half as much as their classmates assumed.

"People thought the popular kids had lots of friends and the brains have no friends, but it turns that everybody had about the same number of friends," said Mitchell Prinstein, another co-author of the paper and a professor at the University of North Carolina at Chapel Hill. (The other co-authors included Sarah W. Helms, Sophia Choukas-Bradley, Laura Widman, and Matteo Giletta.)

Some of the most severe misperceptions—regarding popular kids' cigarette use and jocks' marijuana habits, for example—were within cliques and groupings. Indeed, not only do less-cool kids exaggerate the lifestyles of high school aristocracy, but also popular kids vastly overestimate the sex and drug behavior of other popular kids. An only-slightly-oversimplified summary of the survey might read: Everybody in high school thinks everybody else is having more sex and doing more drugs than they actually are.