A new report is sounding alarm bells about lagging high school graduation rates among students with disabilities.

Some 85 to 90 percent of kids with disabilities are estimated to be capable of completing the requirements for a high school diploma. Yet, just 6 in 10 of these students graduated in 2013, the most recent year for which figures are available.

The findings come from an analysis of federal education data in the annual Grad Nation report released Tuesday, which is produced by the Alliance for Excellent Education, America’s Promise Alliance, Civic Enterprises and the Everyone Graduates Center at Johns Hopkins University.

With the overall graduation rate for American students at its highest ever — reaching 81.4 percent in 2013 — the report finds that some students are struggling to keep pace.

“While progress is substantial in many areas of the country, the number of non-graduates remains disturbingly high for students of color, students from low-income families and young people with disabilities,” wrote Gen. Colin Powell and his wife, Alma Powell, in a letter released as part of the report which their group, America’s Promise Alliance, helped produce.

Among children with disabilities, nearly 62 percent graduated in 2013. The figure reflects an increase over previous years, but still puts those in special education almost 20 points behind the general student population, the report found.

Significantly, graduation rates for students with disabilities varied dramatically across the states, with Arkansas reporting a high of just over 80 percent, while Mississippi came in last at 22.5 percent. The discrepancy is due at least in part to varying allowances for students in special education seeking a standard diploma, the analysis found. In some states, for example, there are fewer credit requirements, extensions or lower performance criteria allowed for these students.

The report also notes that states differ in determining which students with disabilities are counted in this group.

Misconceptions and low expectations as well as discipline disparities likely play a role in lower graduation rates among those with disabilities, the report said.