The report, released Thursday by the Baltimore University's Everyone Graduates Center, found the largest gain was in Tennessee, where the rate rose from 61 percent to 72 percent. New York's rate increased from 64 percent to 67 percent.
Those two states produced the greatest number of additional graduates, with roughly 8,000 more students in each earning high school diplomas in 2006, said the center, which tries to develop strategies to help students graduate.
The Tennessee Department of Education said Democratic Gov. Phil Bredesen had put a lot more funding toward students considered at risk and students for whom English is a second language.
"I have to give a lot of credit to the teachers and principals in the local districts because without them you would not see these results," department spokeswoman Rachel Woods said.
Graduation rates increased by 6.8 percentage in Delaware (to 76 percent) and Kentucky (to 78 percent). 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, 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."