I went to high school in the US in the 1970s. I remember at least three incidents we heard about with students bringing guns to school. No shootings at my school, though. Another school in the same city did have a shooting incident at that time, pissed off student opened fire in shop class.
We (students) knew back then who was disturbed, who would likely carry a gun or knife to school, who might pull a weapon in a cafeteria argument. We all did that "sad calculation" you mention.
When it came time for my own kids to go to school we opted out and homeschooled. Not so much out of fear of mass shootings, but because schools are terrible environments for children in so many ways, and it's easy to do better than what passes for "education" in the US.
We (students) knew back then who was disturbed, who would likely carry a gun or knife to school, who might pull a weapon in a cafeteria argument. We all did that "sad calculation" you mention.
When it came time for my own kids to go to school we opted out and homeschooled. Not so much out of fear of mass shootings, but because schools are terrible environments for children in so many ways, and it's easy to do better than what passes for "education" in the US.