Let's see here, there weren't many school shootings before we started giving out powerful drugs to kids and most of the shooters were taking powerful drugs. It' doesn't take an Einstein to figure this one out.
There weren't many school shootings prior to mothers dosing the unborn in their womb with drugs, either. Neither were there many school shootings prior to weird kid diets. And, let me also mention the lack of school shootings prior to wide availability of drugs among the pre-teen set.