AUSTIN, Texas (AP) -- A new federal study shows that Texas' four-year high school graduation rate climbed to 78.9 percent in 2009-2010, just above the national average but a stark change from previous data that suggested the state was among the country's leaders in on-time graduation.
The Texas Education Agency said the reason for the difference is that Tuesday's report estimates high school attrition rates among ninth graders over four years, while the state tracks actual cases that can adjusted for things like student moving away before finishing high school.
The latest round of data came from the National Center for Education Statistics and showed freshman four-year graduation rates statewide rose from 73.1 percent in 2006-2007 school year to 78.9 percent in 2009-2010. Nationally, the on-time graduation rate was 78.2 percent — the highest since 1976.
Nearly half of America's other states had four-year graduation rates higher than Texas. Vermont led the nation with a 91.4 percent rate, while Nevada was at the bottom with a 57.8 percent rate.
Among Texas Hispanic students, the on-time graduation rate for the Class of 2010 was 77.4 percent, compared to 69.4 percent for blacks and 82.8 percent for whites.
Overall, Texas' dropout rate fell to 2.7 percent for 2009-2010, compared to 3.2 percent the year before. Nationally, the dropout rate was 3.4 percent for the 2009-10 school year, according to the study.
The federal statistics center, which collects and analyzes school data from state and local officials, is run though the U.S. Department of Education.
Its findings were not as stellar as separate, federal Education Department data released in November that showed Texas' four-year graduation rate was 86 percent for the Class of 2011. That mark tied the state with five others for the nation's third-best high school graduation rate — and left top education officials crowing.
The November numbers used a new data reporting system designed to make it easier to compare results across the country.
Texas, which adopted the reporting system several years ago, posted a four-year graduation rate equal to Tennessee, New Hampshire, Indiana, Nebraska and North Dakota. That was a single percentage point behind Vermont and Wisconsin's 87 percent, and Iowa led the nation with 88 percent.
The November numbers were consistent with data from the Texas Education Agency, which reported in August that the four-year graduation rate statewide had reached an all-time high of 85.9 percent for the Class of 2011.
Debbie Ratcliffe, a spokeswoman for the agency, said Tuesday that in addition to measuring separate years, the new federal report differs from November data because it estimates each state's graduation rate based on attrition of ninth graders.
"We're basically counting noses and they're doing an estimate," she said. "The good news is the trend lines for graduates are the same. They're a million different ways to count graduation rates and drop rates, even though there might not seem like it, but as long as they're showing similar trend lines, that's positive."
Ratcliffe said Texas also may have a lower graduation rate in Tuesday's report because the state's population tends to be mobile and many students move out of state before finishing high school.
In its reports to the Department of Education, the state doesn't count such cases against drop-out rates, but the methodology used in Tuesday's study may count some such cases against the attrition rate.