WASHINGTON » High school graduation rates for most states continue to improve, according to preliminary data released Monday by the Obama administration.

The majority of states also are showing gains for black and Hispanic students.

The Education Department says preliminary data indicate 36 states saw higher graduation rates for the 2013-2014 school year. The biggest gains were in Delaware, Alabama, Oregon, West Virginia and Illinois.

Five states had declines: Alaska, Hawaii, Nevada, New Mexico and Oklahoma. The District of Columbia also slipped.

Eight states, the department said, showed no improvement over the previous school year. They were: Colorado, Kansas, Maine, North Dakota, Ohio, Pennsylvania, South Dakota and Texas. Idaho did not have complete numbers to report.

Education Secretary Arne Duncan said the numbers were encouraging.

"By all indications, it looks like the nation will take another step in the right direction in terms of graduation rates," Duncan told reporters. The nation’s overall graduation rate stands at 81 percent, an all-time high.

Final graduation rate data will be released next spring.

The numbers show the District of Columbia with the lowest graduation rate, 61.4 percent. Iowa had the highest at 90.5 percent.

Duncan is retiring from his post in December to return home to Illinois and his family.

John King, who will become acting secretary upon Duncan’s departure, praised state improvements but said, "We still worry that too many kids are trapped in schools that are struggling, and those schools need support to get better."

To help troubled schools, he suggested turnaround programs that focus on professional development or promoting partnerships with community-based groups to meet the outside-of-school needs that might get in the way of learning.