Parents teach their children how to swim, how to ride a bicycle and how to drive. Should they also teach their teenagers how to drink responsibly?

The volatile issue is seldom discussed at alcohol-awareness programs. But some parents do quietly allow their teens to have wine or beer at home occasionally, figuring that kids who drink in moderation with their family may be less likely to binge on their own.

Many other parents argue that underage drinking of any kind is dangerous and illegal, and that parents who allow it are sending an irresponsible message that could set teens up for alcohol abuse in later years.

U.S. government surveys have started tracking where and how teenagers obtain alcohol—and that at least some of the time, parents are the suppliers.

Nearly 6% of 12- to 14-year-olds—some 700,000 middle-schoolers—drank alcohol in the past month. And nearly 45% of them got it free at home, including 16% who obtained it from a parent or guardian, according to a report released last month by the Substance Abuse and Mental Health Services Administration (SAMHSA). The survey doesn't report how much alcohol was involved or what the circumstances were.