Toddler served margarita in sippy cup

In 2002, Elisa Kelly made what she thought was a smart parenting decision. Her son Ryan asked her to buy beer and wine for his 16th-birthday party at the family's Virginia home, promising that no one would leave until morning. Kelly agreed, and to further guard against drunken driving, she collected guests' car keys. But neighbors called police, who arrested Kelly and her ex-husband, George Robinson, for what one official told The Washington Post was the worst case of underage drinking he'd seen in years. Kelly maintained that she was just trying to control drinking that would have gone on whether or not she had bought alcohol for the kids. Both got time in jail; Kelly began her 27-month sentence on June 11.

This graduation season, parents around the country will face a similar dilemma. Should they allow teens to drink under their supervision, or should they follow the law—knowing that their kids are likely to imbibe anyway? Many parents believe teens should learn about drinking at home. Cynthia Garcia Coll, professor of education, psychology and pediatrics at Brown University, grew up in Puerto Rico, where, she says, kids drink at family parties. "Instead, in this country, we go from saying 'No, you can't do it'," and then all at once, we say 'Yes, you can' without really giving them any guidance. It's not like age 21 is a magic time when people become responsible drinkers."

The same reasoning prompted New Yorker Sam Hedrick to offer his three daughters drinks at home. "My youngest is going to be 21 this week," Hedrick says. "She and her friends have had alcohol here with meals." His daughter Lizzie, a student at Bowdoin, 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."

But most researchers who study teen substance abuse say that for every family like the Hedricks, there are many more where allowing alcohol causes problems. "The data is quite clear about teen drinking and it has nothing to do with being puritanical," says William Damon, 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." The antidrinking message is especially critical in families with a history of alcoholism, which greatly increases the risk.

Even if they don't become alcoholics, teens who drink too much may suffer impaired memory and other learning problems, says Aaron White of Duke University Medical Center, who studies adolescent alcohol use. He says parents should think twice about offering alcohol to teens 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."

Girls should be particularly careful, says Dr. Mark Willenbring of the National Institute on Alcohol Abuse and Alcoholism. Women generally weigh less than men and have proportionately more fat and less lean body mass. Because blood circulates primarily to lean body mass, the alcohol is distributed to a smaller volume of tissue, which results in higher blood alcohol levels. "We're absolutely seeing more women competing in drinking games," he says. "That's a terribly dangerous thing to do," in part because they become more vulnerable to sexual assault.

It's also widely believed that youngsters in countries with a lower legal age learn to drink responsibly and moderately. There is one problem with that impression: it is not true. "The highest rate of cirrhosis of the liver is in France," where it's legal to drink at 16, says Chuck Hurley, chief executive officer of Mothers Against Drunk Driving. According to a study by the U.S. Department of Justice, fewer American adolescents drink than teens in most other industrialized countries.

Instead of offering teens a beer, 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. "Parenting is not supposed to be a popularity contest," says Richard Lerner of the Institute for Applied Research in Youth Development at Tufts University. "If the parent is not modeling honest, safe behavior, it's unlikely the kid will believe that he's supposed to act responsibly. You don't want to be like Tony Soprano, who seemed surprised that his son, A.J., was not a model citizen." Someday, your kids will thank you.