sex education!
Common avenues for sex education are parents or caregivers, school programs, and public health campaigns. Almost all U.S. students receive some form of sex education at least once between grades 7 and 12; many schools begin addressing some topics as early as grades 5 or 6.[15] However, what students learn varies widely, because curriculum decisions are so decentralized. Many states have laws governing what is taught in sex education classes or allowing parents to opt out. Some state laws leave curriculum decisions to individual school districts. Abstinence-only sex education tells teenagers that they should be sexually abstinent until marriage and does not provide information about contraception. In the Kaiser study, 34% of high-school principals said their school's main message was abstinence-only.
http://en.wikipedia.org/wiki/Sex_education
