"Some years ago Gary Kleck at Florida State University (look him up) did a survey of National Institute of Justice reports on assaults out side the home. Looking at the outcomes from over 140,000 street crimes, attempting to use a knife was among the highest forms of self defense to likely result in your own hospitalization or death."
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Sounds like a very good reason to avoid using a knife as a self defense weapon. Having witnessed a real knife fight when I was in the army, it's at the top of my list of things to avoid at all costs. LIke RC said, a knife against a gun is going to end badly. A knife against a knife is going to end very very badly.
So what does a high school kid carry to protect himself. Learn to use common everyday objects. A good maglite, AA minimag used as a yawara stick, the padlock on a bandana, metal water bottle, all make decent impact tools. Best of all, use your head to avoid the trouble. Trust your instincts on who to trust and who to avoid. Also, go get some training. I'm sure there are lots of places in Washinton that has martial arts studios with a wide variety of styles.
Just do yourself a favor, and stay away from knives. They make poor weapons and will cause more trouble than they are worth.