The high school graduation rate has improved across Maryland, according to figures released Wednesday, but Prince George’s County saw its graduation rate fall by 3.3 percentage points, leaving the school district more than 10 percentage points behind the state average.

Statewide, numbers for the class of 2012 show that fewer students are dropping out and more are earning diplomas, a mark of progress state officials attributed to Maryland’s steady funding of education and efforts in local districts to address gaps in achievement. Education experts see graduation rates as a key measure of academic success and as an indicator of how well a school system is performing.

Overall, the state’s graduation rate rose 1.5 percentage points over two years, to 83.6 percent for the class of 2012. Montgomery County saw a similar increase, of 1.3 percentage points, to 87.4 percent, and Prince George’s County slipped by 3.3 percentage points, to 72.9 percent.

Prince George’s Chief Academic Officer A. Duane Arbogast said Wednesday that he wasn’t sure how to account for the decline. “I don’t have a strong sense of why it’s not trending with the state,” he said. “I’m a little surprised at the trend data.”

The county has long languished as one of the worst-performing school districts in the state, but it has seen modest improvement in a number of academic measures in recent years. Determined to turn the system around, County Executive Rushern L. Baker III this year engineered an effort to dramatically change school governance, resetting the county school board and hiring a new, highly regarded superintendent. The slip in graduation rates reported Wednesday underscores Baker’s urgency to improve the schools.

Over the past couple of years, Arbogast said, Prince George’s has placed a greater emphasis on programming and supports to help students graduate on time. The district has opened career academies, for example, including a fire cadet program in which students can earn 17 college credits.

Educators in Prince George’s have also been more aggressive in identifying at-risk ninth-graders and designing programs to keep them on track, he said.

“I think a lot of the stuff we have put into practice, it will take time to see the return on investment,” Arbogast said.

The new data follow findings released in January by the National Center for Education Statistics estimating that 78 percent of public school students nationally earned a diploma within four years of starting high school. It was the highest rate since 1974, officials said.

Outperforming the national average were students in Maryland, with a graduation rate of 82.2 percent, and Virginia, with 81.2 percent. The analysis, for the class of 2010, showed the District’s rate was much lower — 59.9 percent — but city figures are difficult to compare with statewide numbers that also reflect suburbs and rural areas.

The new Maryland data on high school graduation was released along with numbers about the state’s drop-out rate, which fell to 10.2 percent. In Montgomery, it fell to 6.8 percent. In Prince George’s, the drop-out rate increased from 15.9 percent in 2010 to 19.5 in 2012.

Arbogast attributed part of Prince George’s increase in drop-outs to changes in reporting methods. He said, for example, if a student leaves the school system to attend another school, the district previously recorded the move as a transfer. Now the state requires districts to have evidence that the child enrolled in another school, he said.

“That’s easy to do if it is in Maryland, harder to do if it’s another state and nearly impossible if it’s another country,” Arbogast said.

Del. Joseline Pena-Melnyk (D-Prince George’s), who has advocated for additional supports for Hispanic students, said she was disappointed by the numbers but not shocked. The rate dropped 2.6 percent for African Americans, 2.7 percent for whites and 8 percent for Hispanics between 2010 and 2012.

“I have been pushing for more resources to treat every child, not just Hispanic children, holistically,” she said. “The numbers show something is wrong. We are not reaching them.”

In Montgomery, the four-year graduation rate showed small, steady increases of 0.6 percentage points compared to the previous year and 1.3 percentage points over two years. African American students showed the largest improvement, with a jump of 4.2 percentage points over two years.

With a continuing focus on the achievement gap in Montgomery, the new state numbers showed progress in narrowing the divide between white and African American students and between white and Hispanic students.

Still, the most recent four-year graduation rate in Montgomery is 95.2 percent for Asian students; 94 percent for white students; 82.3 percent for black students; and 76.7 for Hispanic students.

Montgomery School Board President Christopher Barclay called the gap a critical issue and said Montgomery has a long way to go. “We are improving, but we are far from meeting the real goal, which is parity,” he said.

Barclay attributed improvement to a combination of “young people being more clear about the importance of their education” and educators increasingly recognizing the importance of making school relevant to student lives.

“It has to be more engaging,” he said. “It has to be more exciting. As we get better at that, I think you will see graduation rates go up.”