Imagine for a moment that you’re a parent with a teenage son. He doesn’t drink, but you know his friends do. You’re also not naive. You’ve read the government’s statistics: 47 percent of high school students tell researchers they’ve had a drink of alcohol in the previous 30 days. Thirty percent have had at least five drinks in a row in the past month. Thirteen percent admitted to having driven in the previous month after drinking alcohol.

So, what do you do with regard to your son’s social life? Many parents have decided to take a realist’s approach. They’re throwing parties for their kids and their friends. They serve alcohol at these parties, but they also collect car keys to make sure no one drives home until the next morning. Their logic makes sense: The kids are going to drink; it’s better that they do it in a controlled, supervised environment.

That’s exactly what a Rhode Island couple did in 2004. When they learned that their son planned to celebrate the prom with a booze bash at a beach 40 miles away, William and Patricia Anderson instead threw a supervised party for him and his friends at their home. They served alcohol, but William Anderson stationed himself at the party’s entrance and collected keys from every teen who showed. No one who came to the party could leave until the next morning.

For this the Andersons found themselves arrested and charged with supplying alcohol to minors. The case ignited a fiery debate that eventually spilled onto the front page of the Wall Street Journal. The local chapter of Mothers Against Drunk Driving oddly decided to make an example of William Anderson, a man who probably did more to keep drunk teens off the road that night than most Providence-area parents.

In fact, the Andersons were lucky. A couple in Virginia was recently sentenced to 27 months in jail for throwing a supervised party for their son’s 16th birthday, at which beer was made available. That was reduced on appeal from the eight-year sentenced imposed by the trial judge. The local MADD president said she was “pleasantly surprised” at the original eight-year verdict, and “applauded” the judge’s efforts.

In the Washington area, several civic groups, public health organizations and government agencies have teamed up for a campaign called Party Safe 2005. You may have heard the ads on local radio stations in prom season, warning parents that law enforcement would be taking a zero-tolerance approach to underage drinking. The commercials explicitly said that even supervised parties — such as those where parents collect the keys of partygoers — wouldn’t be spared. Parents would risk jail time and a fine of $1,000 per underage drinker.

Not only do such uncompromising approaches do little to make our roads safer, they often make them worse. The data don’t lie. High school kids drink, particularly during prom season. We might not be comfortable with that, but it’s going to happen. It always has. The question, then, is do we want them drinking in their cars, in parking lots, in vacant lots and in rented motel rooms? Or do we want them drinking at parties with adult supervision, where they’re denied access to the roads once they enter?

The Virginia case mentioned above is troubling for another reason: The cops raided that home without a search warrant. This is becoming more and more common in jurisdictions with particularly militant approaches to underage drinking. A prosecutor in Wisconsin popularized the practice in the late 1990s when he authorized deputies to enter private residences without warrants, “by force, if necessary,” when there was the slightest suspicion of underage drinking. For such “innovative” approaches, Paul Bucher won plaudits from Mothers Against Drunk Driving, which awarded him a place in the “Prosecutors as Partners” honor roll on the MADD Web site.

The Post reported a while back on a party in Bethesda in which there was no underage drinking at all. Police approached the parents at a backyard graduation party and asked if they could administer breath tests to underage guests. The mother refused. So the cops cordoned off the block and administered breath tests to each kid as he or she left the party. Not a single underage guest had been drinking. The police then began writing traffic tickets for all of the cars around the house hosting the party. The mother told the Post, “It almost seemed like they were angry that they didn’t find anything.”

Surely there are more pressing concerns for the Washington area criminal justice system to address than parents who throw supervised parties for high school kids. These parents are at least involved enough in their kids’ lives to know that underage drinking goes on and to take steps to prevent that reality from becoming harmful. We ought to be encouraging that kind of thing, not arresting people for it.