"significant positive behavioral outcomes...such as delayed onset of sexual activity, reduced levels of early sexual activity, and fewer sexual partners among adolescents."
None of the remaining 5 studies found any negative results (indicating that the effect is at worst neutral), and some reported positive findings that just fell short of statistical significance.
The Heritage Foundation report also discussed the methodological flaws of the much-publicized Mathematica study, which claimed there were no significant differences between students who received abstinence-only education and those in control groups.
The Centers for Disease Control also this week reported that share of all U.S. pregnancies accounted for by teens has declined from 15% in 1990 to 12% in 2004. The abortion rate for teens has dropped by 24% over the same time frame.
Unfortunately, critics of abstinence-only education such as Planned Parenthood are lobbying Congress hard to kill Federal funding for these effective programs :-( Of course, they have a financial conflict of interest when it comes to pushing contraceptives since 50% of all unplanned pregnancies are the result of contraceptive failure and nearly half of those will end in abortion. The more teens who abstain from sex, the less money PP will make from providing abortions...