"Many of the programs were in a stage of early development when the evaluation occurred," wrote Robert Rector, senior research fellow at the Heritage Foundation, a conservative think tank, in a critique of the report. He added that the fact that participants in the programs were quite young, and follow-up education was lacking could have contributed to the failure.
"The main lesson that should be taken from this study is that interventions at a very early age require significant follow-up, or they'll be less likely to alter teen risk behaviors," he wrote.
Some critics have also maintained that the lack of high school programs in the study shows that the study is not representative of the overall impact of this funding. Indeed, two of the programs focused on upper elementary school students and the other two, on middle school students. None of the four included a high school component.
Trenholm says these criticisms overlook the fact that most of the money earmarked for these programs does not go to high school programs anyway.
"We went where the funding went," Trenholm says. "Virtually every program taking funding was at the middle school and elementary levels, and not at the high school level."
Proponents of abstinence-only sex education programs maintain that "comprehensive" sex-education programs -- those that introduce ideas of safe sex in addition to abstinence -- are untested and may not yield any better results.
"I don't think that this is quite true," Kempner says, adding that programs that go beyond abstinence have yet to receive the same federal funding and support enjoyed by their abstinence-only counterparts.
"We don't have any money," she says. "We need some money and some time like the abstinence-only people got."
Kempner adds that promising research backs up comprehensive programs.
"We have some good research suggesting that comprehensive programs are effective," she says. "I think that we will have much more support on comprehensive sex education, and I think this study will be a part of it."
Davidson argues that such programs could put more responsibility in the hands of the teens themselves, allowing them "make much better decisions" when it comes to sex.
"Abstinence-only education treats smart, thoughtful teens as if they are incapable of absorbing information or understanding themselves," she says.
"If government officials finally understand how important it is that young people receive complete and accurate sex information, whatever the cost of this study, it will have been worth it. It's time that people wake up."
The report also included a hint of good news about teen sex in the United States.
"On the other side, we also did not see any increase in unprotected sex," Trenholm says, adding that many researchers had expected to see a spike in unsafe sex due to the fact that existing programs do not cover the proper use of birth control.
This, as well as other evidence uncovered in the study, suggests that peer relationships are particularly important when it comes to predicting abstinence -- an area for future study, Trenholm says.
"The idea is that future programs may want to seek out, build and maintain peer relations through clubs and other groups," Trenholm says. "In this way, I think it's suggestive of a good direction for the field to go in."