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.
In the 70's we used to laugh about saying "high school" because there were so many drugs floating around at school. Guess what, we had no school shooters and the most you could get from the school nurse was an asprin.