It's bad to bring a knife to school.
It is the morning and it's Mark's birthday today and before school his mother has given him a Swiss Army Knife as a gift.
Mark wants to store the knife somewhere.
Mark stores the knife in his sock drawer at home before going off to school.
Mark stores the knife in his school backpack and ends up taking it to school with him.
Mark comes home later and happily plays with his new shiny, red knife.
The principal finds Mark with his knife and expels Mark from school for having weapons.