Sex Education is classroom instruction on human reproduction and sexuality. It is typically taught by both public and private schools, with parents usually given the option of withdrawing their children if they feel the content to be inappropriate or have personal or religious objections.
The appropriate content for sex education is a subject of political dispute within the United States, and within other countries. The greatest division is between the comprehensive and abstinence-only schools of thought. Proponents of comprehensive sex education believe that instruction should include education on methods of contraception, as a means to prevent the twin threats of pregnancy and the transmission of sexually-transmitted infections. Proponents of abstinence education maintain that instructing unmarried teenagers on contraception is implicitly endorsing sexual activity outside of marriage, and so sex education should omit contraception and instead concentrate on helping teenagers to avoid pressure towards pre-marital sexual activity, and to wait until they are in a monogamous, married relationship to begin sexual activity.
As well as subjects directly related to physical sexual acts, sex education may also include instruction or guidance on relationship management, self-control, pregnancy, the physiological changes of puberty, sexual orientation, and sometimes the morality of sex. This variety adds to the political controversy, with varying groups advocating the inclusion or exclusion of specific components.
Sex education is typically taught at varying points throughout education, either as a separate short course (often with a visiting specialist teacher) or as a module in the science curriculum. Thus an individual student will go through several sex education courses, each one imparting information considered appropriate for their age at the time.
Federal funding for abstinence only education across the country has increased during the decade, but still does not equal the amount of money the government gives to Planned Parenthood, a single organization, each year.
It should be noted that, while teens can benefit from abstinence-only sex ed in school, prudent parents may still want to take the precaution of informing their children of basic contraception. No matter how strong the will to resist one's physical urges, it cannot be denied that some children will inevitably give in to their desires and that they ought to know how to prevent unplanned pregnancy in this eventuality.
Sex Education in England
In England the National Curriculum  requires all schools to offer comprehensive sex education as part of Personal, Social and Health Education, from junior school on. These classes are opt-out: All children take the lessons unless their parents have previously requested otherwise.