Abstinence Only Education - Does it work?

In 2 of my feeds, there was an article on abstinence - so it must be ground breaking. According to the version of the article that I read, they used 662 African American middle school students and sent some to a weekend-long abstience only program. They were also paid $20 for their time.
The results: "...only about a third of the students who participated in a weekend abstinence-only class started having sex within the next 24 months, compared with about half who were randomly assigned instead to general health information classes, or classes teaching only safer sex. Among those assigned to comprehensive sex-education classes, covering both abstinence and safer sex, about 42 percent began having sex." This is the first abstience-only study that has seen these positive results.

http://www.nytimes.com/2010/02/03/education/03abstinence.html?partner=rss&emc=rss

I think that this is great. I 'm glad that these kids decided to wait a while before having sex. However, I feel that part of their decision to pay attention during the workshop was the influence of the $20 that they were given to participate. And once they started becoming "sexually active" did they use birth control?
I understand that some religions (such as mine) are proponents of abstience-only. However, what happens once they do start having sex? Aren't they at higher risk for pregnancy and STDs?