In my school days the city kids had to go home for lunch. The country kids brought a sack lunch and ate at the school.
Knives can be used as tools, such as an eating utensil. A stone on your desk can be a paperweight, or thrown as a weapon. This is a total lack of common sense.
I remember one day in Jr. High, word got around that a science teacher who was an amateur archeologist, collected old military weapons, uniforms etc.. He brought in a WW-II Thompson sub-machine gun and we all went to his classroom to look it over and hold it. Imagine that today.