While it is true that all but one of these events have occurred in a public school, to stress it as a public vs private school phenomenon is too simplistic. All of the public schools involved have been ones where attendance is mandatory. Violence, at least of this magnitude, is rare in the thousands of the nation's 86,000 public schools that are small, and none of these fifteen have occurred there. More to the point, thousands of them, whatever their size, are schools of choice such as magnet schools and charter schools. Everyone, staff and student alike, is there voluntarily.
Most schools of choice are small.
A federal study of charter schools concluded that the average size of new ones is 137 students - larger ones tend to be converted public schools. People creating a school for themselves do not create large ones. Literally hundreds of studies have consistently found that large schools are less effective and more dangerous than small ones. In addition to the research, we have now repeatedly been given living, or dying, proof.