First tip I can say is, do not be afraid to talk to your kid about it. Your child will freak out if he/she knows that you know about the drinking, they will calm down if you handle it correctly.

Second, Grounding, yelling, or otherwise trying to discipline your child about drinking solves nothing. In most cases, this causes the minor to drink more in an act of rebelling against you.

Third, inform your kid what can happen to him/her if they drink. Show photos of car crashes, medical pictures, etc. This curbs drinking a lot if they know truly what will happen if they continue. Talk to them and ask why they do it, fitting in with the other kids is high on the list, thou depression can be a reason. If it is depression or issues in the home, take the child to see a professional so he/she can better deal with the issues that are causing the drinking. It might take time but most kids will stop.

Just keep on loving your child and show them that you care.