Two very large problems with this analysis:

1) if you read it, it excludes acts of terror and government. So the Chechen school where 186 kids were massacred isn’t included, nor are attacks on schools elsewhere.

2) It only goes through 2009 (they quote it as through 2010; the actual study says 2009). Not clear if it includes the Winnenden shooting. Certain it does not includes this years attacks in Chinese schools that have left 21 dead and many more wounded.