When you're under the age of 21, it is not legal for you to drink over a certain amount of alcohol and be behind the wheel of a vehicle. However, that doesn't mean you're never allowed to drink or that you're completely banned from consuming alcohol in public. While the legal drinking age is 21, there are exceptions to every rule.
People who are under the age of 21 usually cannot be on a premises that is licensed to sell alcohol. However, if they are with guardians, spouses of legal drinking age or their parents, the licensee may decide that it's appropriate for them to be at the venue. In those cases, the individuals may also possess and consume alcoholic beverages with their parents.
Keep in mind that the owner of the facility has the right to deny those under the age of 21 alcohol of any form. Many business owners will not want to serve those under 21 despite it being legal, because they could be convicted of felonies if the underage individual leaves the facility and causes a collision or harm to others.
Although it is not always illegal for those under 21 to drink, the legal limit to be behind the wheel is still standardized. Those under 21 should never drink and drive, because any amount of alcohol in their systems could draw suspicion and lead to a charge. In those cases, the parents of the underage person or the minor him or herself will need a strong defense to stand up for the minor's rights and good character.
Source: Revenue.WI.gov, "Alcohol Beverage Laws for Retailers - Underage Alcohol Questions," accessed Sep. 29, 2017