Studies about teen sexuality are irresistible media bait, and for good reason: parents are interested because they’re worried about their kids’ well-being, teens are riveted because they want to know how they compare with their peers, and the rest of us just want to see if our youthful antics (or lack thereof) measure up to today’s standards.

The latest installment in the Sex Lives of the Young and the Restless comes from Johns Hopkins University. In a study, “Patient Teenagers? A Comparison of the Sexual Behavior of Virginity Pledgers and Matched Non-pledgers,” published in Pediatrics this month, the authors show that teenagers who take virginity engage in sexual activity before marriage at the same rate as teens who don’t pledge, or, in social science speak: “Pledgers and matched nonpledgers did not differ in premarital sex, sexually transmitted diseases, and anal and oral sex variables.”

A slew of news outlets, including The Washington Post, the Chicago Tribune, Bloomberg, and others jumped on the story, touting its findings.

Yesterday, Wall Street Journal “Main Street” columnist William McGurn chided these outlets for overlooking a fine point of the research—that the pledging and non-pledging teens both came from religious backgrounds, and, in fact, as a group were much more behaviorally conservative than the general population of teenagers.

McGurn tips his hat to U.S. News & World Report “Heart to Heart” columnist Bernadine Healy, who first pointed out the subtlety:

In the study, it was only when researchers closely matched the virginity-pledging young people with a subset of nonpledging teens of similar social and attitudinal backgrounds that the two groups’ sexual behaviors were similar—and both those groups were more conservative than teens overall. This matchup was important in that it showed that the greater sexual restraint of the pledging teens, demonstrated here and in most other studies, was not due to the pledge per se but rather other virginity-promoting factors in their backgrounds. In fact, most of the pledgers forgot that they had ever made such a promise about sex before marriage.

Approximately three quarters of both pledging teens and the matched group of teens who didn’t pledge had had sexual intercourse before marriage, but both groups reported less premarital vaginal sex, as well as less oral and anal sex, and fewer of them had had multiple sex partners when compared with the general population of young people.

The takeaway for parents, Healy says, is to pursue a holistic approach, not a one-time shot deal: “The focus should be on cultivating the teenager’s ongoing home and social environment, rather than on eliciting a one-time, easily forgotten promise.”

The Wall Street Journal is right to call foul on the press for oversimplifying the story and playing down the substantial differences between the religious teens in the study and the rest. But McGurn fails to mention one of the study’s key conclusions: that teenagers from conservatively religious backgrounds tend to forego birth control when they do have sex, leading to greater incidence of teenage pregnancy and sexually transmitted diseases. The New Yorker’s Margaret Talbot explored this dichotomy in November:

Pledgers delay sex eighteen months longer than non-pledgers, and have fewer partners. Yet, according to the sociologists Peter Bearman, of Columbia University, and Hannah Brückner, of Yale, communities with high rates of pledging also have high rates of S.T.D.s. This could be because more teens pledge in communities where they perceive more danger from sex (in which case the pledge is doing some good); or it could be because fewer people in these communities use condoms when they break the pledge.

Bearman and Brückner have also identified a peculiar dilemma: in some schools, if too many teens pledge, the effort basically collapses. Pledgers apparently gather strength from the sense that they are an embattled minority; once their numbers exceed thirty per cent, and proclaimed chastity becomes the norm, that special identity is lost. With such a fragile formula, it’s hard to imagine how educators can ever get it right: once the self-proclaimed virgin clique hits the thirty-one-per-cent mark, suddenly it’s Sodom and Gomorrah.

Katia Bachko is on staff at The New Yorker.