American society, and it's people, are quite different today than when I was a kid.
For example, it used to be that violence on airplanes was unheard of (other than terrorist hijackings). Now, it's becoming more and more frequent. I don't fly, but if I did I would feel safer knowing that everyone else went through a metal detector and didn't have any knives on them. When's the last time you heard of a person being stabbed on a plane?
Also, when I was a kid in school the worst a student might do in class is talk or throw a balled up piece of paper at another kid. No one ever heard of a kid bringing a gun to school and shooting their fellow students, teachers, etc.
I have two teachers in my family, and I've head many horror stories of just how bad some kids are today. They have no discipline in their lives, they have no self-control, and they act out violently against other students and staff.
Throughout all my years in school I never heard of one student stabbing another, but that was a different time. Today, with what I know about what goes on in US schools, I don't disagree with prohibitions on kids having knives at school. Your kid might be responsible, but what about the little sociopath who sits behind him/her. Sure it's possible for kids to bring weapons to school regardless of rules or laws prohibiting it, but that doesn't mean the schools, or the laws, have to permit it.
I know this is a knife forum, and some, or many here might be of the opinion that people should be able to carry any knife they want anywhere they want, but things have gotten pretty crazy out there.
And I have no issue with laws prohibiting knives in courthouses or on the grounds of correctional institutions.
With the exceptions of schools, airplanes, courthouses and correctional institutions, I think people should be permitted to carry any knife they want, openly or concealed, anywhere in public. But I also believe that owners of private property (like sports venues or amusement parks, etc) should have the right to enact and enforce policies against possessing knives on their property. I'm a big believer in the rights of private property owners.