Adolescent sexuality in the United States - Most common reasons virgins cite for remaining abstinent

Epidemiologists at the Center for Disease Control emphasize that for sex education to be effective, it should take place before teens become sexually active.

Reference 1: Fear of pregnancy, Fear of STDs, Decision to wait until marriage, Belief that sex was not right for a person their age and Parents would object.

Reference 2: Percent of 9th grade males, Percent of 12th grade males, Percent of 9th grade females and Percent of 12th grade females.

Source: http://en.wikipedia.org/wiki/Adolescent_sexuality_in_the_United_States