Alcohol use by persons under age 21 years is a major public health problem. Alcohol is the most commonly used and abused drug among youth in the United States, more than tobacco and illicit drugs, and is 
responsible for more than 4,300 annual deaths among underage youth. Although drinking by persons under the age of 21 is illegal, people aged 12 to 20 years drink 11% of all alcohol consumed in the United States. More than 90% of this alcohol is consumed in the form of binge drinks. On average, underage drinkers consume more drinks per drinking occasion than adult drinkers. In 2010, there were approximately 189,000 emergency rooms visits by persons under age 21 for injuries and other conditions linked to alcohol.
Prevention of Underage Drinking
Reducing underage drinking will require community-based efforts to monitor the activities of youth and decrease youth access to alcohol. Recent publications by the Surgeon General1 and the Institute of Medicine outlined many prevention strategies that will require actions on the national, state, and local levels, such as enforcement of minimum legal drinking age laws, national media campaigns targeting youth and adults, increasing alcohol excise taxes, reducing youth exposure to alcohol advertising, and development of comprehensive community-based programs. These efforts will require continued research and evaluation to determine their success and to improve their effectiveness.
Source: http://www.cdc.gov/alcohol/fact-sheets/underage-drinking.htm