In 1996, concern over the high teen pregnancy rate led Congress to include legislation in its Welfare Reform Act allocating $50 million over five years to states that agree to teach abstinence-only education programs in the nation’s public schools. Schools that accept the funds must instruct students that “abstinence from sexual activity is the only certain way to avoid out-of-wedlock pregnancy, sexually transmitted diseases, and other associated health problems.” To ensure that students receive the abstinence-only message, the legislation prohibits schools from using the grant money to teach students about contraceptives or how to protect themselves from sexually transmitted diseases.

Advocates of the abstinence-only program contend that teaching students to say “no” to sex is the most effective way to reduce the teen sex and teen pregnancy rates and to reduce the spread of sexually transmitted...