In a society as flooded with sexual imagery and provocative content as ours, there is perhaps little surprise in the statistics about teenage sexual activity and its effects. Still, anyone with children or grandchildren in school might want to sit down before reading any further.

The U.S. Centers for Disease Control estimates that nearly 48 percent of American teens have had sexual intercourse. But the 2007 Youth Risk Behavior Survey that yielded the statistic has even more alarming news than that. One in 10 American boys and almost one in 20 girls have had sex before the age of 13. Fully 15 percent of school-age children reported they had had intercourse with four or more people in their lifetimes.

Considering the exhaustive evidence that early sexual activity is inherently unhealthy on both a physical and an emotional level, the numbers are chilling. A 2005 study published in the American Journal of Preventive Medicine showed that teen girls who had sex were up to three times more likely to be depressed a year later than those who didn’t. And one teen girl in three will get pregnant at least once before the age of 20, according to the National Campaign to Reduce Teen Pregnancy.

Kids might not realize it, but most adults do: Early sexual activity often has painful consequences that can last a lifetime.

Amid the videos, the television programs, the explicit music lyrics, the magazine ads — and, of course, the Internet — many teens are unable to see the truth of those consequences and are desperate for illumination. That’s where Lighthouse Outreach comes in.

The nonprofit organization is training teachers in Suffolk’s middle schools to present a program on abstinence, which remains the only foolproof way of avoiding pregnancy, sexually transmitted diseases and the heartbreak that can come from sexual activity by children whose emotional development hasn’t yet reached a point to equip them for the non-physical side of intimate relations.

Middle school might seem a bit early to embark on such a program, but sex education — especially the unofficial kind — often starts even earlier. Unfortunately, not even programs like the one offered by Lighthouse are foolproof. Parents still need to be involved with and supportive of their children. They must still supervise their teens and keep them involved in church and other community activities. And they must make it clear that they expect their children to abstain from sexual activities.

Teenagers have made stupid choices ever since the first hormones raged in the first 15-year-old. But your kids — and our society — are relying on you to help them learn how to make the right ones. OK, now, get up and go have that talk. It really can’t wait.