About one-third of America’s eighth-grade students, and about one in four high school seniors, are proficient writers, according to results of a nationwide test released on Thursday.

The test, administered last year, showed that there were modest increases in the writing skills of low-performing students since the last time a similar exam was given, in 2002. But the skills of high-performing eighth and 12th graders remained flat or declined.

Girls far outperformed boys in the test, with 41 percent of eighth-grade girls scoring at or above the proficient level, compared with 20 percent of eighth-grade boys.

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). Those two and seventeen other states ranked above New York, where 31 percent of students wrote at the proficient level.