It would be nice to think New York is the only state with this problem, but it’s not. A lot of states have been using sleight of hand on tests and proficiency rates to make themselves look better than they are. It’s part of the whole pathology in education governance around looking good rather than doing well.
You’re hearing a lot of excited chatter about how common standards will make this problem go away. That’s wrong. The same political and optical pressures will exert themselves in a new venue, which is why the governance and fidelity requirements around the new common core are the ballgame, not just how many states decide to adopt.
Lay primer on cut scores here (pdf). You can see how (a) easy it is to get into mischief here and (b) how a new set of standards isn’t a cure by itself.