The department on Wednesday released rankings that for the first time compare states using the same data.
Vermont had the third-best graduation rate, at 87 percent, while New Hampshire ranked seventh with an 86 percent rate. Maine came in 10th, at 84 percent.
Iowa had the highest graduation rate, 88 percent, while the District of Columbia had the lowest rate, 59 percent.
The ranking method essentially bases the rates on students who enter school as ninth-graders and graduate within four years, according to reports. The approach allows for direct comparisons among states.