http://en.wikipedia.org/wiki/Bath_School_disaster
1927.
There were 38 kids killed and 6 adults. The author has his facts wrong.
People are natural born killers. No brag, just fact.
A lot has to do with the modern media and fixation on violence combined with their desire to promote their agenda.
My great grandmother once told me about a shooting at a one room school in a neighboring township when she was a child in the very early 1900s.
There are some 30+ separate school buildings in my county and I can’t find that even one has ever had a shooting. There are better than 100,000 separate school buildings nationwide.
I do think there are some things that need to be taken into account like the modern public school model that creates a large pool of potential victims. There is also the culture of subjective morality that infects the American educational system.