A recently released report from the Thomas B. Fordham Institute does an excellent job summarizing the confusion and debate regarding graduation rates as well as thoroughly describing the current set of metrics. Setting aside for a moment the question of whether graduation rate is the right metric to indicate preparedness for post-high school success, it's imperative that there is clarity in the definiton of any metric used so widely. 

Unless and until a standard definition is used by all parites, it will remain extremely difficult to assess just what on-time high school graduation does and doesn't tell us about the desired outcome: preparing students for success in life.  Hopefully the renewed push for definitional clarity described in this report will take root.