The nation’s high school graduation has been climbing steadily for nearly a decade, but the overall trend masks wide differences among states and groups of students.

Low-income students, black and Hispanic students and students with disabilities are still far less likely to graduate than average, according to the annual GradNation report released Tuesday by a coalition of groups pushing to raise the national graduation rate to 90 percent by 2020.

“We are running out of time to close large and lingering gaps in graduation rates among different student populations,” Gen. Colin L. Powell and Alma Powell of America’s Promise Alliance, part of the GradNation coalition, wrote in a letter introducing the report.

In 2013, 81.4 percent of all students graduated within four years, according to the latest federal data. That’s up 1.4 percentage points from the year before.

But some states saw far larger-than-average gains (California, Florida, Georgia and North Carolina) while others stagnated or even slid backward (New York, Illinois, Washington and Arizona).

Minority students have been closing gaps with their white peers, but the gaps are still substantial: Among white students, 86.6 percent of students graduated on time, compared with 75.2 percent of Hispanic students and 70.7 percent of black students.

Economically disadvantaged children trail their more affluent counterparts by more than 15 percentage points. Among low-income students, 73.3 percent graduated on time in 2013, compared to 88.2 percent for students not considered low-income.

Again, states have widely different records of improving their disadvantaged students’ chances of graduating on time.

Graduation rates among low-income students, for example, range from a low of 59.5 percent in Alaska to 85.4 percent in Kentucky.

Kentucky is an example of what’s possible, according to the GradNation report: It has virtually erased the gap between its low-income and more affluent students.

The two maps below show how prevalent that gap is across most of the country.

This map shows graduation rates of non-low-income children. Most states are either light green (more than 85 percent graduate on time) or dark green (more than 90 percent graduate on time).

The map below shows graduation rates of low-income students, and the contrast is clear: Most of the country is pink, meaning that fewer than 80 percent of low-income students are graduating on time. Kentucky and Texas stand out as exceptions:

Kentucky has been successful in part because it was among the first states to get serious about holding schools and school districts accountable for graduation rates, according to one co-author of the report, John Bridgeland, president of Civic Enterprises.

Progress on graduation rates plays into evaluations for Kentucky’s principals and superintendents, Bridgeland said. Schools are using early warning systems to identify which students are at-risk of dropping out, Bridgeland said, and then they are intervening with academic, social and community supports.

Kentucky’s black and Hispanic students are also doing better than the national average for those groups. Bridgeland said in a future report, GradNation is planning to dig deeper into Kentucky’s success to see if there are lessons that can be applied elsewhere.

“I like the particularity with which Kentucky has been focused on graduation rate accountability,” Bridgeland said. “Graduating students ready for college has been job number one.”