this may sound slightly insane, but....
I don't think kids should be allowed to drop out at all - although if a state allows it, they could be homeschooled and the like.
However, everyone should be required to get a HS diploma - if they have mental issues they should receive extra help, and if they are prone to not giving a damn they should be required to at least meet minimum standards.
If they refuse, they also should recieve extra help, but in a different form, up to and including armed guards locking them in a classroom until they either die or learn.
Ok that last bit might be SLIGHTLY overkill. :mrgreen:
Edit: Further, I would fully support a law that requires parents to attend some meetings between the parents, the teacher, and the kid.
And by requires I mean if you don't show up an arrest warrant is issued and the police can drag your ass there. Pay the parents for their time if necessary, assuming their financial situation is that desperate. And don't allow them to be fired for not being at work during such a meeting.
Man, I'm turning into a totalitarian or something...