"How to track high school graduation rates has been a contentious issue for years, with states using different methods to come up with a number. Balfanz cited that as a reason why the report does not include the names of the dropout factories. He said they will be included in a future report once all states are consistently reporting data.

States are now required to use the same method to compute graduation rates based on a Bush administration rule issued in 2008.

Nevada stood out for its low graduation rate of 56 percent, a decline of more than 15 percentage points from 2002 to 2009, the largest of any state, the report said...."



From here: http://www.lvrj.com/news/report-nevada-stands-out-for-low-graduation-rate-143288706.html



I believe the number is from dropout who left in a given year.

For youngsters who were enrolled at sometime in their four years of high school age, dropout rate is more than 50%.