This report from the Guardian UK on abstinence only sex education is troubling:
A survey of more than 2,000 teenagers carried out by a research company on behalf of Congress found that the half of the sample given abstinence-only education displayed exactly the same predilection for sex as those who had received conventional sex education in which contraception was discussed.
Mathematica Policy Research sampled teenagers with an average age of 16 from a cross-section of communities in Florida, Wisconsin, Mississippi and Virginia. Both control groups had the same breakdown of behaviour: 23% in both sets had had sex in the previous year and always used a condom, 17% had sex only sometimes using a condom; and 4% had sex never using one. About a quarter of each group had had sex with three or more partners.
Basically, the study says it doesn't matter what you tell kids about sex -- the outcome is the same. Abstinence-only doesn't work; neither does comprehensive sex ed.