Tennessee's high school graduation rate improved more than any other state's in a new report by researchers at Johns Hopkins University.

While the national high school graduation rate remained flat at about 75 percent between 2002 and 2006, the Volunteer State is one of a dozen states that made substantial gains, according to the report, released Thursday by the university's Everyone Graduates Center.

"It's really a tribute to the hard work of teachers in each school in Tennessee," said Rachel Woods, spokeswoman for the Tennessee Department of Education. "Those are the ones really making the difference."

Ms. Woods said the study used federal graduation statistics, and the rate the state calculates was even higher than the one reflected in the study.

The Tennessee rate rose from 61 percent to 72 percent, according to the study. New York showed the second biggest increase, climbing from 64 percent to 67 percent.

Red Bank High School Principal Gail Chuy agreed with Ms. Woods, praising teachers.

"Our teachers work very, very hard to make sure students keep up with the material," she said. "We just give every opportunity in the world for the child to succeed, and I think that's probably true across the state."

Ms. Chuy said the rate increase shows a value in the state's curriculum.

"I think it says a lot for not just keeping kids in school but making school mean something and making it relevant," she said.

Tennessee and New York produced the greatest number of additional graduates, with roughly 8,000 more students in each state earning high school diplomas in 2006, said the center, which tries to develop strategies to help students graduate.

Tennessee Gov. Phil Bredesen, a Democrat, had put a lot more funding toward students considered at risk and students for whom English is a second language, according to the Tennessee Department of Education.

"I think there are a number of policies Gov. Bredesen put into place that are paying off and show in this report," Ms. Woods said.

Graduation rates increased by 6.8 percentage in Delaware (to 76 percent) and Kentucky (to 78 percent), according to the study. Rounding out the list of states with substantial gains were South Dakota, Arkansas, Alabama, North Carolina, Hawaii, Missouri, Nebraska and New Hampshire.

The report comes just days after President Barack Obama's first major speech on education, in which he discussed reducing the high school dropout rate and pushing states to adopt more rigorous academic standards.

"One can look at the national data and get kind of depressed and think we're not improving, but we need to look at the fact that there are 12 states that did make significant improvements," said Robert Balfanz, co-director of the Everyone Graduates Center. "But we're still clearly not putting enough resources and know-how behind this critical national problem."

Staff Writer Andy Johns and The Associated Press contributed to this story.