DIFFERENT WAYS of calculating graduation rates allow school districts to kid themselves and the public about how many students succeed in getting diplomas. Even though the new calculation of graduation rates for D.C. high school students shows depressingly low numbers, the move to get a clear-eyed diagnosis must be applauded. Only by laying bare the problem can it be solved.

Using a more rigorous method being mandated by the federal government, the Office of the State Superintendent of Education released figures last month showing that 58.6 percent of the 5,058 students in the city’s charter and traditional high schools graduated in 2011 within four years. The rate for the class of 2010 under the old formula was reported at 73 percent, a drop that shows just how much the failure to track ninth-graders throughout their high school years inflated and distorted the results. “With the new calculations,” D.C. Schools Chancellor Kaya Henderson said in a statement, “we have a clearer understanding of the work we will need to do, and the public has a more reliable way to hold us accountable.

Even as the numbers outline the sobering deficiencies of D.C. public education, there was encouraging news. The school system is moving in the right direction; The Post’s Bill Turque reported that if the old formula had been used to compute the 2011 rate, there would have been a seven-point increase over 2010. New efforts are being made to identify and counsel students at risk. Attention to simple details such as students’ schedules is paying dividends. Officials set the ambitious goal of a graduation rate of 75 percent by 2017.

Particularly noteworthy was the performance of the city’s public charter schools. They posted an overall graduation rate of about 80 percent, considerably higher than the school system’s overall rate of 53 percent (the system’s application high schools posted a rate of 86 percent, with Banneker showing an impressive 100 percent). Of the 10 schools with the worst graduation records, seven are run by the school system; the worst is Cardozo, with a graduation rate of 39.9 percent.

Critics were quick to suggest that charters have figured out how to get students at risk of dropping out to transfer to traditional schools. Charter officials dispute that, noting that less than 5 percent of children in public charters depart each year and most either leave the area or enroll in other charters. A better explanation is charters’ extra efforts in creating a culture where college and career are expectations for all students. Now that the scope of the District’s poor record on graduation is known, it’s all the more urgent that solutions be found.