The Department of Education is once again disagreeing with the conclusions of an annual report on graduation rates across the country, which puts Hawaii in the bottom third of states for the number of students who leave school with a diploma.

The "Diploma Counts" report, released today, says Hawaii’s graduation rate is 65.8 percent — lower than the national average of 71.7 percent and far below Hawaii’s calculated graduation rate of 80 percent.

The discrepancy between the report’s rate and the state’s calculation is linked to differences in how researchers arrive at graduation rates — an argument that’s expected to quiet greatly this fall, when the federal government will for the first time require states to calculate graduation rates in the same way.

The method states will use — called an adjusted cohort rate — is almost identical to Hawaii’s formula. The big difference will be that Hawaii will have to count transfer-in students, where before it had only followed a ninth-grade cohort from the first day of their freshman year to graduation.

Hawaii and 22 other states currently use some variation of the cohort rate, according to the Diploma Counts report, which used a different method to calculate graduation rates.

The department has long argued the report’s calculated graduation rates are inaccurate and unfair. The cohort rate "is the purest form and process" of calculating a graduation rate, said Glenn Hirata, administrator of the DOE’s system evaluation and reporting section.

The authors of Diplomas Count 2011 — annually produced by the nonprofit Editorial Project in Education, which publishes Education Week — pointed out that every state reported a different graduation rate from the one arrived at in the study.

Washington, D.C., which does not use a cohort rate, saw the biggest difference. Officials there said their graduation rate was 75.5 percent, while the report calculated it as 43 percent, the lowest in the nation.

Nevada had a slightly higher rate, with 44.3 percent, according to the report. New Mexico came in third from the bottom, with a 57.1 graduation rate.

Meanwhile, New Jersey had the highest graduation rate in the report, with 86.9 percent, followed by Vermont (82.7 percent) and Wisconsin (81.3 percent).

Hawaii’s graduation rate of 65.8 in the report came in 11th from the bottom, flanked by Alaska (66.3 percent) and Washington state (65.6).

The report points out that Hawaii’s graduation rate, as it’s calculated in the study, has increased by nearly 6 percentage points over the last decade.