First, I'm going to observe in passing that, this is kind of a funny place to have this debate, and I'm really interested in the outcome. Seems to me more than one forumite celebrated multiple 19th birthdays, back in the day.
Long post, but what it boils down to is this: I see that there is a problem with lying about age from a social standpoint. I think it's a gray area, and try to balance my teen's needs and maturity against the rules. I then try to explain my decision-making process to my daughter, because she's less likely to do an end run around me if she understands that maybe it's not based on her maturity level, but out of consideration for other people or other factors.