Suffolk Public Schools administration and teachers are cheering another measured improvement in the division’s on-time graduation rate.

Each of the city’s public high schools improved its graduation rate, a statistic that tracks each year’s ninth-graders to see how many of them graduate four years later. Still, one in five high school students in Suffolk are failing to finish the 12th grade on time, according to statistics recently released by the Virginia Department of Education.

“We’re improving each time,” said Kevin Alston, assistant superintendent for administrative services. “It’s encouraging that we’re making improvement, but any time you have any students drop out or don’t graduate on time, that’s not good.”

The division-wide on-time graduation rate for Suffolk’s class of 2010 was 79.8 percent as reported by the education department. Alston said a handful of students have been tracked down since the data was reported, and those corrections would bring the actual rate to slightly more than 80 percent. The dropout rate is about 12 percent once adjusted for those students, he said. The remaining 8 percent or so are students who are still in school, are on long-term medical leaves or for some other reason have not yet finished.

Both numbers are an improvement from last year, when the state reported a 77.6-percent on-time graduation rate and a 12.6-percent dropout rate for the city.

Alston attributed the improvements to better record-keeping to track where students go once they leave the system, as well as additional remediation programs to help struggling students keep up with their peers.

“We keep adding programs,” Alston said. “The main thing is keeping kids on grade level. Once they fail, the chances of failing again are pretty good.”

Examples of such programs include the Z-block program at Lakeland High School, which offers students who are falling behind the chance to attend “credit recovery” classes for two extra hours after school. Another program allows those struggling only in English or math to continue on with their classmates while doubling up to catch up in their most difficult subject.

Comparing the three high schools, Nansemond River came out on top for the third straight year with an on-time graduation rate of 86.8 percent. That was a small improvement over 2009, when its rate was 86 percent.

Lakeland High School had the biggest year-over-year improvement among the three schools with its rate of 81.5 percent — an increase from its 2009 rate of 76.2 percent.

King’s Fork High School came in this year with a rate of 72.6, compared to last year’s 71.9-percent rate.