Most sexually active teenagers had sexual intercourse for the first time in their parents' homes, late at night, according to a report conducted by Child Trends researchers and released today, the AP/Houston Chronicle reports. Researchers said that the study, which analyzed data from the National Longitudinal Survey of Youth, should "dispel myths" that teens most often have sex after school, when parents are at work. Based on the national survey, which has tracked 8,000 children ages 12 to 16 since 1997, the study looked specifically at the 664 teens who reported having had sexual intercourse for the first time between 1999 and 2000. The study found that 56% of those surveyed in 2000 said they first had sex at their family's home or at the family home of a partner; 12% said at a friend's house; 9% said at their own home; 4% said in a vehicle; 3% said at an outdoor location; 3% said at a hotel or motel; and 10% said at another location. In addition, 42% said they first had sex between 10 p.m. and 7 a.m., and 28% said between 6 p.m. and 10 p.m. Only 15% of respondents said that they had sex for the first time between 3 p.m. and 6 p.m., before their parents arrived home from work, the AP/Chronicle reports. The study also found that 34% of teens have had sexual intercourse by ninth grade, and 60% have had sex by 12th grade. The survey did not examine whether teens were having sex on weeknights or weekends and did not ask if parents were home at the time of the sexual encounter. National Campaign to Prevent Teen Pregnancy Director Sarah Brown said the study shows that parents "can have a significant impact on their children's decisions about sex," the AP/Chronicle reports. She added, "This notion that it's impossible to supervise kids is ludicrous if a lot of them are having sex in the rec room" (AP/Houston Chronicle, 9/26).