I can remember the exact point in time that knives became antithetical to my society. the year was 1982, and I was a ninth grader in a small, norther Minnesota school. Up until this point, it was very common for young men to carry about on their person a small/medium pocket knife. The single bladed, wood handled with brass bolster buck knives were very popular, as were a variety of SAKs. At no time did anyone take exception to this practice.
This particular year, we had a new vice principal. A decidedly liberal individual who was shrouded in scandal. Rumor had it that she had to leave her big city (Minneapolis) HS administration job because she had an affair with a married teacher. [incidentally, she eventually managed to break up two marriages in our small town, where divorce was still considered a grave exception to the rule]
Back to the point... While in the office with one of my friends to use the phone, one of the office ladies asked my friend if she could borrow his knife to cut some heavy tape. When my friend handed her his SAK, the vise principal about had a cow. She started screaming "Security! Security!" Of course, there was no security, but a 911 call brought the city police rolling in about 30 minutes later. By then, my friend, myself, 2 teachers, and about 15 other "criminals" were standing by waiting to be incarcerated on illicit weapons charges. We were never charged, but I never did get that Buck Knife back, and the practice of carrying knives to school came to a screeching halt.
I would venture that there is not a public school in the country today that would admit to letting students (or teachers for that matter) freely carry knives on school grounds.