I'm clearly in the minority opinion here. I've said my piece. I've been called names. I'll just call this a loss and move the fuck on. I admit my response is mostly emotional. I feel for anyone who gets bullied, I got bullied too. I got called names, got threatened, all that fun stuff. From the time I was 8 up to about 16. I have massive social anxiety issues that I attribute to that treatment. But a lot of people I considered assholes, bullies, people who made my life downright unpleasant? They've grown up to be average, generally law abiding college students. Not a god damned one of them deserved to die for their behavior.
I think this kid could have found a better way to handle the situation. Borrow a cell phone, buy cheap pepper spray (yes, a school would prohibit it but any knife capable of nicking the heart probably violates school regulation too), not leave school, punch the kid in the throat (yes, it could kill too, I know)...I don't know. Maybe it was the only answer he could see. But stabbing a person in the heart...that can't be the absolute best answer to a high school fight.