Seems to me that 1) they would be better served to sue the government for something that is definitely going to cause them to suffer loss in the future, such as the massive annual deficits and the currently humongous federal debt, and 2) they probably don't have much of a case, since they can't prove that the losses will actually materialize. Seems likely you can only sue if you've actually BEEN harmed, not because you think you're GOING TO BE harmed.
Of course, they're stupid teenagers, being put up to it by their teachers/parents, I'm sure, and as such they don't understand that. Great publicity for their (incredibly stupid?) lawyers, though.