I am with Ladyblue and others with 18. If you are old enough to be cannon fodder for your country, you're old enough to make an informed decision about drinking. Focus should be on education.
Or even better
b: We should raise the age for a disadvantaged youth (who is too young to drink) to join the armed forces and maybe go die in the Middle East because that's the only way s/he will be able to get a proper education and better themselves and their families. After all, if they are not considered old enough to make good decisions about drink, they are definitely not old enough to make a decision about dying or getting scarred for life.......hmm