The Virginia Department of Education on Tuesday confirmed an announcement earlier this month by the Suffolk Public Schools system that the division’s dropout and on-time graduation rates had improved across the board in the past year.

Suffolk school administrators released preliminary numbers reflecting improvement in the two key tracking indices during their October School Board meeting.

The final numbers released Tuesday by the state’s education department are actually slightly better than had been expected, showing improvement in both student retention and on-time graduation at all three of Suffolk’s public high schools.

On a division-wide level, the city’s on-time graduation rate — which measures the percentage of students who earn some kind of high school diploma within four years — improved from 72 percent in 2008 to 77.8 percent in 2009.

The division’s dropout rate, which reflects the percentage of students who leave school without a diploma, fell from 19 percent in 2008 to 12.6 percent in 2009.

“This is significant progress to be made in one year,” School Superintendent Milton Liverman said during the School Board meeting earlier this month.

In fact, the city’s new number put it about in the middle of the pack amongst Hampton Roads school systems.

Suffolk falls behind Chesapeake, Virginia Beach and Isle of Wight with its on-time graduation rate of 77.8 percent. Franklin, Norfolk and Portsmouth all have on-time graduation rates below Suffolk’s.

The city’s updated dropout rate is still more than twice that of Virginia Beach, Hampton Roads’ leader in the category with a rate of only 6 percent. Suffolk also trails Chesapeake, Isle of Wight and Norfolk in dropout prevention. But its 12.6-percent rate is well below that of Franklin (19 percent) and Portsmouth (20.1 percent).

The city’s school system still has some improving to do before catching up with state averages, though. Virginia’s overall on-time graduation rate was 83.2 percent in the most recent report, and its dropout rate was 7.9 percent.

The state’s on-time graduation rate rose 1 percentage point from the previous year.

“Building a long-term trend of rising graduation rates will require a continued student-by-student approach by educators, as well as the sustained involvement of parents and strong partnerships with community institutions,” Virginia Superintendent of Public Instruction Patricia I. Wright stated in a release announcing the new figures.

Among Suffolk’s high schools, Nansemond River led the way, with an 86.2-percent on-time graduation rate and a 6.3-percent dropout rate. Lakeland posted an on-time graduation rate of 76.2 percent and a dropout rate of 13.8 percent. King’s Fork High School also improved from last year, but it posted the worst results, with a 72.4-percent on-time graduation rate and a 16.6-percent dropout rate.