U.S. students graduated from public high schools at the highest rate since the 1970s, with the largest leap for Hispanic students, government data show.

In 2009-2010, 78.2 percent of students earned a diploma after four years, compared with 75.5 percent the year before, according to a U.S. Education Department report released today.

President Barack Obama’s administration, many states and education and business groups have been pushing to improve high- school graduation rates, which stagnated in the 1970s, 1980s and 1990s and fell behind the nation’s economic rivals. While the government said the reasons for the improvement aren’t clear, researchers credited elementary school preparation and better tracking of potential dropouts.

“It’s incredibly important,” Bob Wise, the former governor of West Virginia, said in a phone interview. “This is hard work, and there’s some progress being made.”

Wise’s Alliance for Excellent Education, a Washington - based advocacy group focused on improving graduation rates, estimates that the 1.3 million high school dropouts from the Class of 2010 cost the U.S. economy $337 billion in lost wages over their lifetime.

To discourage dropouts, school districts have instituted early-warning systems to track students, flagging absenteeism or failing grades in English and math, said BethAnn Berliner, a senior researcher with WestEd, a San Francisco-based research organization that works with states and schools.

‘Dropout Factories’
 

The Obama administration has pushed states to institute student-tracking systems and improve graduation rates through its $5 billion Race to the Top grants and other programs aimed at turning around the worst-performing schools, often called “dropout factories.”

Efforts to identify and improve those schools, which educate a disproportionate share of immigrant and other minority children, may be starting to pay off, according to Patricia Gandara, an education professor who co-directs the Civil Rights Project at the University of California, Los Angeles.

The government rate estimates the percentage of high-school students who graduate within four years of first starting ninth grade. It includes only those who earn a standard diploma, not a lesser certificate or equivalency degree.

In 1969-1970, the rate was 78.7 percent. It fell as low as 71 percent in the 1990s, before inching higher in the current decade.

Ethnic Groups
 

In the most recent round, Asian-American students had the best performance, at 93.5 percent, trailed by whites at 83 percent. The Hispanic graduation rate of 71.4 percent rose from 65.9 percent, the largest increase of any ethnic group. For blacks, the percentage rose to 66.1 percent from 63.5 percent.

The new report doesn’t offer reasons for the improvement, said Jack Buckley, commissioner of the National Center for Education Statistics, which collects the data. It could result from a weak economy, which makes it less likely for teenagers to leave school for work, he said in a press briefing.

Steady, recent improvement undercuts that explanation, said Richard Murnane, a Harvard University economist and education professor who has studied graduation rates.

It’s more likely a result of significantly improved achievement in elementary grades among the lowest-performing students, Murnane said. National standardized math test scores have been rising for those students over the last 10 or 15 years, he said in a phone interview. To a lesser extent, they have risen in reading, as well.

“Kids are getting to high school a little more prepared to do high-school work,” Murnane said.