14% to 37% of 15-year-olds say they've had sex
Countries like the Netherlands with robust sex-education programs and teen access to contraceptives have the highest teen use of birth control and the lowest teen pregnancy rates, according to a survey of 33,943 adolescents from 24 European and North American countries. About 82% of sexually active teens report using contraceptives.
Santelli, J., et al. (2008). Contraceptive Use by 15-Year-Old Students at Their Last Sexual Intercourse.Archives of Pediatrics and Adolescent Medicine, 162(1):66-73.