No idea.  I was a pretty short tempered kid and quick to swing.  I don't recall getting in a fight in Kindergarten, but I know I attacked a teacher because I thought the strawberries my mother sent with me were for my lunch.  Shoulda known that bitch would never make me lunch.  I really loved strawberries.  Still do, just not enough to attack someone for it.   I know I was constantly in trouble for fighting even in elementary right thru high school.  Many of my fights were against older kids simply because I was never one to be pushed around, no matter the "rank".  I won some, I loss some.  But I will never fear a man.  A woman, on the other hand...  Whew, can't live with 'em...  What?  That's it.  Can't live with 'em.   
I started teaching my daughter to fight before she ever went to school.  Of course, this caused some problems when she finally went to a day care.  Let's just say, you didn't piss her off if you were another kid and it cost me a couple daycares.  I had to teach her to dial it back and not to be physical unless she had no choice and was being physically assaulted.  It worked, but that's another story.