While some parents are fine letting adolescents drink at home under their supervision, researchers say parents should think twice about such a plan. “The data is quite clear about teen drinking, and it has nothing to do with being puritanical,” says the director of the Stanford University Center on Adolescence. “The earlier a kid starts drinking, the more likely they are to have problems with alcohol in their life.”

Caution is especially critical in families with a history of alcoholism, which greatly increases the risk. Even if they don't become alcoholics, teenagers who drink too much may suffer impaired memory and other learning problems, says an official from the Duke University Medical Center who studies adolescent alcohol use. Parents, he says, shouldn’t offer alcohol to teenagers because their brains are still developing and are more susceptible to damage than adult brains. “If you’re going to do that, I suggest you teach them to roll joints, too,” he says, “because the science is clear that alcohol is more dangerous than marijuana.”

Still, many parents believe adolescents should learn about drinking at home. One father offers his three daughters drinks at home. “My youngest is going to be 21 this week,” he says. “She and her friends have had alcohol here with meals.” His daughter agrees with her father. “If your parents are so against alcohol from the start when you’re younger, you’re never exposed, and it just becomes this enigmatic, forbidden thing,” she says. “I can understand why it seems cool.”

Instead of offering teenagers a beer, researchers say, parents should present their children with clear rules and expectations. Research shows that involved parents are less likely to raise kids with drinking problems. Give them strategies for avoiding trouble, like telling them to call home for a ride rather than getting into a car with someone who has been drinking. Most important, be a good role model.