I just got off the Miracle yesterday and saw quite a few people who, by the looks of things, were not over 21. I never saw a bar waiter ask for ID.
I'm not sure but there may be differences on a minors S&S card, making it easy for waiters to spot them. Maybe not, I'm not sure.
If you look like youre over 21, you might have some luck. If not, prepare to be disappointed.
Right now most schools are in session and kids are not on ships. If you cruise now, they probably wont ID and you should be ok. My thought is that if you go during their peak party season, they will enforce the policy moreso than they would now.