Because Google and sociology, education, and psychology classes?
http://www.advocatesforyouth.org/pu...413-adolescent-sexual-behavior-i-demographics
"Many adults are uncomfortable with the idea of teen sexuality, and prefer to remain in ignorance or denial. But in the United States, 46 percent of all high school age students, and 62 percent of high school seniors, have had sexual intercourse; almost nine million teens have already had sex.1,2 It is critically important for adults to address adolescent sexuality realistically and to recognize that many factors, including socioeconomic status, race or ethnicity, family structure, educational aspirations, and life experiences, affect young people's behavior..."
"For several sub-populations of adolescents, comparatively little data is available. Existing evidence indicates that these youth exhibit behaviors or live in environments which place them at higher than average risk for HIV, other sexually transmitted infections (STIs), unintended pregnancy, sexual abuse, and other preventable sexual health problems. These populations include LGBT youth; rural youth; youth with disabilities; certain immigrant youth; runaway, homeless, and "street" youth in unstable living situations; youth living with HIV; and youth in the custody of the foster care or juvenile justice systems. Until there is more nationally-representative data about such youth, policy makers and program planners will face challenges when seeking to promote the sexual health and well-being of these young people..."
"Adolescents who can envision positive futures for themselves are more likely to maintain healthier sexual behaviors and to avoid or reduce sexual risk-taking, but there are racial and ethnic disparities that delineate young people's ability to perceive positive futures. One analysis used data from Add Health to study the "future certainty" of 5,900 teens (mean age 16) and to identify disparities among White, African American, and Hispanic youth. Findings showed that White youth held the most positive perceptions of life certainty (defined as living beyond age 21 and surviving to at least age 35), college certainty, and marriage certainty. Furthermore, youth with the most positive life, college, and marriage certainty also had the highest levels of sexual knowledge..."
