I believe the drinking age on Princess ships and all cruise line ships is 21. I do not hink if your parent or gaurdian signs for you that you can purchase wine or beer. I am sure those parents or gaurdians will buy liquor for those teens and that creates many, many problems with teen drunken behaviour. This seems to cause a lot of teen children problems on many cruise lines.
on Princess ships --the drinking age is 21. Minors sign and sail card will have a hole punched on them telling the servers that they are under-age and cannot purchase liquor. If i recall minors cannot even get into the disco-(they can only get in on certain nights).