The article in question can be downloaded from Pediatrics, here.
The final “wave 3” data came from the group that the author calls “adolescents” — who were 22 years old. Data from those who had married was treated as “missing.”
We don’t know anything about the actual sex ed courses that the students took, who paid for the course, or whether they actually took a course or just made a pledge.
From the article: “Virginity pledges are also now used to measure AOSE program effectiveness, which the US government considers successful if they produce many virginity pledgers, irrespective of participants’ sexual behavior.”
(Is it true that the pledge is considered a marker for the success of abstinence-only sex ed? I know that I’ve read several articles showing short term increase in the intention to remain abstinent, so that would not surprise me. However, I haven’t seen this “marker.”)
As far as I can tell, it appears that the author took data from a series of national questionnaires , matched kids for background and family, and found that they have similar outcomes after 5 years.
Oddly, a huge number – 80% – of the pledgers denied having pledged in follow up. The other number that seems to stick out is that the non-pledgers did pay for sex and/or get paid for sex more often.
Nevertheless, the only study that I’ve seen that measured pregnancy rates after a course that included teaching proper condom use did not show prevention of pregnancy, either. I posted a review of the pay-for-view article in the British Medical Journal.