??? um...that seems to be more than enough from my experience in CT, i imagine NYC would be even more liberal with the cancellations. It depends on road conditions obviously. But almost all schools were cancelled here for the last storm across the state, even the shore and most places only got 2-4, with 0.5-2 at the coast.
It all depends on timing. If we get 6-12 the night before and it ends at 4AM, there probably will be a 2 hour delay. If the forecast is for 2-4 or even 1-3 and its snowing at 5-9am, schools will be closed.