Drop 21 benchmarks to 20 or 19 and push the 18 benchmarks up to the same number. Either count as an adult or don't.
There's the "You can be drafted and die for your country but you can't drink" argument (though in some places you can drink while you're in the army on the base or somthing IIRC)
The problem is that if you do that, at 18 you're still a dependent but you're in college. This probably already happens but it'd be a LOT more common.. You'd either have to add more high school (NO THANKS) or drop it to 18, not 19.
I've already stated my opinion and IIRC one person at least agrees with me.
Poll