On-time graduation for students with a disability in Suffolk Public Schools has nosedived, according to official figures released Tuesday by the state Department of Education.

The subgroup’s district-wide 2012 on-time graduation rate was 73.6 percent, a sharp fall from 80.3 percent in 2011, district Assistant Superintendent for Administrative Services Kevin Alston said.

Almost a quarter of the 110 disabled seniors in Suffolk’s public schools who would have been in the class of 2012 dropped out, a 38-percent rise from 2011.

Both numbers are off par from the statewide average of about 10 percent of disabled students dropping out and an on-time graduation rate of nearly 85 percent.

“Hopefully we’re going to recover next year,” said Alston, who hopes the poor result for students with a disability is a temporary “blip.”

He noted that the subgroup’s dropout rate has improved since 2008, when it was about 33 percent.

Antoine Hickman, the district’s director of special education, said he could find no cut programs that could have contributed to the poor result for disabled students.

In other data released by the Virginia Department of Education Tuesday, Suffolk’s 2012 district-wide on-time graduation rate of 84.1 percent was minutely better than early data presented to the School Board this month suggested.

“The only reason it changed is because we found another graduate,” Alston said.

At 9.9 percent, meanwhile, dropouts fared slightly worse than the district’s early data. The Suffolk rates lag behind statewide data by almost 4 percentage points for on-time graduation and more than 3 percentage points for dropouts.

But the official data also yielded some good results for the Suffolk district, including improved on-time graduation rates for blacks and Hispanics slightly above statewide rates.

The 83.6 percent 2012 rate for black Suffolk public school students is a welcome improvement from about 80 percent in 2011, Alston said.

He also noted that slightly more than 80 percent of the district’s male seniors graduated on time this year, which is an improvement of almost five percentage points from 2011.

Of Suffolk’s three public high schools, Alston said that Lakeland has “really made some strides.”

Part-time graduation coaches at King’s Fork and Lakeland have been credited with helping improve rates, and the board has said it will look to fund one full-time position for each high school.

Alston suggested that for students who repeat earlier grades, perhaps coaches should intervene before the senior year.