Officials have no explanation for why there has been a leveling off after years of steady progress; a decade ago, less than half the students in District schools graduated on time.
Until this year, officials counted graduates based on the high school where they started 9th grade. This year, they began calculating the graduation rate based on the school a student last attended. So students who leave for charter schools, private schools, or other school districts no longer figure in the overall rates.
In the accompanying chart, the District retroactively applied the new methodology to all the classes going back to the 2006 first-time 9th graders.
There are still gaps in graduation rates based on race, ethnicity, and gender, some of them striking. Except for two groups, graduation rates have only slightly fluctuated. They seem to have declined significantly for Hispanic males and increased for White females. Officials had no explanations for these changes.