Do I have a case for defamation of character/slander?

My school principal calls me in falsely accuses me of using marijuana because they found marijuana in the cl room near my desk. Searches me and my book bag, tells other principles, and a few of my teacher now know. When I said it wasn't mine he called me a liar and threatened me with explosion and reporting me to the police. Now everyone at school knows about this. I look like a complete druggy, although the principle did not put me in any trouble yet do I have a case against him for defamation of character/slander?