A recent article in the New York Times highlights modest increases in the writing skills of below-average students, but it also mentions that the skills of above-average students plateaued or declined. Regardless, more NJ students scored above the proficient level than any other state. According to the Times, "New Jersey and Connecticut were the two top-performing states, with
more than half their students scoring at or above the proficient level
(56 percent in New Jersey, 53 percent in Connecticut)."

The full article can be found here: In Test, Few Students are Proficient Writers