The study, published in Health Education and Behavior, found nearly 1 in 6 sixth-graders is already an alcohol user.

First author Keryn Pasch of the University of Minnesota School of Public Health said many of the users of alcohol in elementary school believe "drinking is normal."

"Children who use alcohol in sixth grade respond differently to messages about alcohol use than those have not used alcohol," Pasch said in a statement. "By sixth grade it's too late; we'll miss many of the at-risk kids."

The study compared sixth-graders who had used alcohol in the past year to those who had not, in a multiethnic, urban sample of more than 4,000 students in 61 Chicago schools. Seventeen percent of the sample were found to have used alcohol within the past year.

The study found the alcohol users more likely to be male, engage in violent or delinquent behavior, have friends who used alcohol, lack the confidence to refuse alcohol and fail to perceive the negative consequences of alcohol.