The reason kids can't carry knives into schools is that they will use them on each other and on teachers/staff.
Sad/disgusting that "society" or "civilization" has digressed so far and so rapidly.
When I was in school (1960~1974 school years) starting the first or second grade, it was taken for granted by the school district, school administrators, teachers, and I suppose law enforcement, that all the boys had
at least one pocketknife in their pocket, and (I'm guessing) 97% of the girls had a pocketknife and/or a paring knife (in a cereal box cardboard sheath) and/or pointed scissors in their purse. (I believe all the girls I knew did. No one asked, since it was considered "rude" to do so.
For "Show & Tell" during grades 1 to 3 inclusive, students brought in the "normal" things like stamp and baseball card collections, pet birds and spiders, fishing rods and reels, Boy/Cub/Girl Scout stuff.
Quite a few of us (and not just the boys) brought in our (not our parent's/grandparent's) .22 rimfire rifle (or .410/28/20 guage) shotgun starting at age six or seven. BB/Pellet guns were also popular.
A few of my classmates had a .22 revolver they brought in for show & tell.
Guess what? No one raised an eyebrow when a 1st to 3rd grader brought a knife or gun to school!
Oor when high schooler's who hunted had a shotgun and/or bow for deer hunting, or a shotgun and/or .22 rifle for upland game in the rear window of their pickup or the rear side window of their Blazer/Bronco/Scout, or station wagon. Others had their hunting arms in the trunk of their car.)
When there was a fight at school, no one pulled a knife or went to get their gun or bow.
Never had a school shooting or stabbing.
Schools weren't virtual prisons then, enclosed by high fences topped with barbwire/razor wire, all the doors were unlocked during school hours. The buildings, grounds, and parking lots weren't patrolled by armed security guards. There were no metal detectors and armed security checking ID's and for weapons at all the entrances, either.
Those in High School even had "Open Campus" able to leave during the periods they didn't have a class, returning for their later class(es) if any, if they didn't want to go to the school library to study, or go to the commons to hang with friends, snack, and play cards. Some (with the instructor's permission) spent extra time in whatever vocational shop class they were taking (carpentry, auto mechanics, welding, machine shop, and drafting) putting in extra time when the lower/starting classes were in session, working on their own projects, and helping teach the younger students, during their free period(s) Oh, If you were in a wood, auto mechanics, welding, or machine shop class part of the unofficial dress code for that class was a Buck 110 or two blade slipjoint folding hunter, or a Puma lockback be on your belt.
The official dress code for shop students (excluding drafting) was safety glasses, short sleeve shirts, long pants or bib overalls, and steel toe safety boots or shoes are required. Along with necessary for the class safety equipment, such as welders gloves, welding cap, welding helmet, and cutting goggles, when engaged in those activities. A leather shop apron was never frowned upon, but wasn't required. (good thing. those were and are not inexpensive.)
No loose neckties or bolo/string ties. Clip-on neckties (if they got caught in a rotating part it would be ripped off - not choke the wearer to death before the machine could be shut down or the tie cut) and bowties were allowed
Oh, none of the schools I attended had uniforms.
The dress code was pretty much "No nudity. Shirt/pants or shorts and shoes (Blouse or halter top, pants/shorts or dress or skirt and shoes for the girls) required."
All of the schools I attended were non-segregated. Everyone got along, no matter what color someones shell happened to be.
I attended school in Iowa, graduated in '74
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My daughter attended school in South West Missouri. Her experiences were like mine. No one cared what shell color someone had. (my daughter is "mixed race")
One of the required courses to graduate at her school for both the guys and girls was the NRA Hunter Safety Course!
She graduated in '95 or '96.
Rifles, shotguns, and archery equipment in the windows of student's vehicles didn't raise eyebrows in Missouri, either.
I won't give my opinion on why civilization has fallen so far in so little time. This forum isn't the place for that discussion.