A new study in the British Medical Journal confirms prior research indicating that abstinence-only education has no effect, positive or negative, on sexual behavior. As critics have long maintained, this review of available empirical research indicates that abstinence-only education does not prevent teenagers from having sex or reduce the incidence of sexually transmitted diseases. At the same time, and contrary to the claims of some critics, abstinence-only education does not appear to increase the rate of unprotected sexual activity. In other words, whether or not children receive abstinence-only education or more comprehensive sex education appears to make no difference at all.
If the BMJ analysis is correct, it would suggest that the raging political fights over the form and content of sex education in schools are purely ideological, not scientific. Both proponents and opponents of abstinence-only education claim that "science" supports their preferred approach, when the available scientific research suggests there really is not much difference.
Here is some BBC coverage of the study, and here is an informative episode of Justice Talking on abstinence education from several weeks back.
UPDATE/CORRECTION: As some commenters observed, it is an overstatement to say that this research suggests that no form of sex education can affect sexual behavior.