U.S. high school graduation rates are at an all-time high. (Kenneth C. Zirkel/iStock)

The national high school graduation rate hit an all-time high in 2013-2014, with 82 percent of students earning a diploma on time, according to federal data released Tuesday.

The data shows that every category of student — broken down by race, income, learning disabilities and whether they are English-language learners — has posted annual progress in graduation rates since 2010, when states adopted a uniform method of calculating those rates.

“This gives me a real sense of optimism of where we can go over the next few years,” Education Secretary Arne Duncan told reporters. “For far too long in this country . . . clearly there was a sense in far too many places people didn’t honestly believe in their hearts that black and brown children could be successful. We’ve gone, as a nation, from having 2,000 dropout factories to 1,000. That’s still not zero, but we cut that in half.”

The difference in graduation rates between white students and their black and Latino peers is narrowing, said Duncan, who is stepping down at the end of the month. “Students of color are improving faster than white students. That’s very encouraging. It means we’re closing the gaps.”

School districts that made the greatest progress closely tracked student academic performance early, not waiting for a student to reach 11th or 12th grade before realizing there was a problem, Duncan said.

“Many schools are focusing on the freshmen, on the first six weeks, with a laser-like focus of making sure students are staying on track,” he said.

But disparities persist.

In 2013-2014, 87.2 percent of white students graduated on time, compared with 72.5 percent of African Americans and 76.3 percent of Hispanics. Asian Americans had the highest graduation rate, at 89.4 percent. The rate was 74.6 percent for low-income students, 62.6 percent for English-language learners and 63.1 percent for students with disabilities.

The data, collected by the National Center for Education Statistics, estimated the graduation rate by dividing the number of high school graduates in a class by the number of students who entered that class as freshmen four years earlier, with some adjustments made for transfers.

Graduation rates can vary widely from state to state. For example, just 18.1 percent of English-language learners graduated on time in Arizona, compared with 84.1 percent in Arkansas. In Texas, 84.2 percent of black students graduated on time, while in Nevada the rate was 53.9 percent.

Locally, Maryland (86.4 percent) and Virginia (85.3 percent) were above average. The District had a graduation rate below the national average, at 61.4 percent.

The state with the highest graduation rate was Iowa, where 90.5 percent of the Class of 2014 graduated on time. The District posted a lower rate than any of the states.

The only thing preventing more schools and districts from improving rates is “a lack of urgency, a lack of creativity and, frankly, a lack of strategy,” Duncan said.

High school graduation rates are one measure of school success, but experts caution about placing too much value on them because graduation requirements are set locally and can change over time, making comparisons across jurisdictions difficult.

To judge progress, Duncan said the public needs to consider four data points: high school graduation rates, dropout rates, the percentage of high school graduates who need to take remedial classes when they begin college and the college graduation rate.

“You need all these things, you need checks and balances, multiple measures,” Duncan said.