Today, May 3—in case you didn't know it—is "National Day To Prevent Teen Pregnancy." In the past decade, possibly no social program has been as dramatically effective as the effort to reduce teen pregnancy, and no results so uniformly celebrated. Between 1990 and 2000 the U.S. teen pregnancy rate plummeted by 28 percent, dropping from 117 to 84 pregnancies per 1,000 women aged 15-19. Births to teenagers are also down, as are teen abortion rates. It's an achievement so profound and so heartening that left and right are eager to take credit for it, and both can probably do so. Child-health advocates generally acknowledge that liberal sex education and conservative abstinence initiatives are both to thank for the fact that fewer teenagers are ending up in school bathroom stalls sobbing over the results of a home pregnancy test.

Read the full article. From the sound of the rest of it, the real reason for the lack of pregnancies isn't that teens are more responsible and either use condoms or don't have sex, but that the little swimmers don't swim so good.

Maybe a comparison of teen STD rates is in order.
UPDATE here's the comparison data from the CDC. While the gonorrhea rate is down, the syphilis rate is up and the chlamydia rate is basically unchanged. The fundamental upshot seems to be teen pregnancy is down because male fertility is for shit, and not because of education or abstinance.

Sperm counts and teen pregnancy rates. By Liza Mundy