"You have to care to give up your afternoons and Saturdays to work with kids to make sure they have a high school diploma," he said.

Baltimore City noted improvements as well. The percentage of students who graduated in four years rose to 68.5 percent in 2013. And the percentage of students who dropped out declined by 2 percentage points to 12 percent.

The city data represented a significant improvement compared to three years ago, when 23 percent of the class of 2010 dropped out and about 61 percent of students graduated.

Interim city schools CEO Tisha Edwards said in a statement that the progress was encouraging amid increased rigor in the school district with the implementation of the Common Core standards. "Our students are posting gains that are promising," she said. "The tools we need are in place."

Other Baltimore area counties saw mixed results. About 94 percent of Carroll County's Class of 2013 graduated, down from more than 95 percent the previous year, while graduation rates for Hispanic and black students saw significant increases. Harford County's graduation rate reached 89.5 in 2013, a 1 percentage point increase from the year before. Anne Arundel County's graduation rate remained steady at about 85.5 percent.

Balfanz said he believed the state's improved rates reflect that the students started high school during poor economic times and may have been more motived to stay in school.

Bill Reinhard, a spokesman for the state Department of Education, agreed that the economy was a factor.

"Students and their parents understand more and more each day that a high school diploma is the bare minimum requirement for a job," Reinhard said.

Changes in the way that federal and state governments calculate graduation rates and the emphasis on reporting more accurate data may also have contributed to the increase.

Balfanz said he believed the federal government alerting states in 2008 that they would soon be held accountable for graduation made a difference. For the first time this past school year, Maryland began to put more pressure on schools to improve their graduation and dropout rates by giving that data more weight in the state accountability system.

That, Lowery said, may have made high schools focus more intently. "I am a firm believer in what gets measured gets done," she said.