Just to throw this out there, cause I only casually glanced over some of the comments...
I took a knife to school. I took a knife everywhere. I just didn't get caught. Carrying a knife is sometimes a good thing to do, for numerous reasons. It's a handy tool and an easily concealable weapon for defense.
While the repercussions of getting caught sucks, I wouldn't exactly blame "carrying a knife". However if he was showing it off and bragging about it, then that's the height of stupidity.
On another note, since my family was broke as fuck, I'd sell things at school to get lunch money, which could have gotten me in a lot more trouble had I ever been caught than simply having a knife.