Topic: How much truth do you put into your writing?

"Writers write what they know." I've always heard that. Stephen Kings says, "Fiction is the truth inside the lie."
For the sake of discussion, how much "truth" do you put into your fictional writing? How much of yourself is part of your characters?
For example: I had a student say the words that follow to me. AND I had books thrown at me in the classroom, though I was never actually hit. I took a small real-life incident and let my imagination run to create Lucky Thirteen.

Dupree burst out laughing. “You a scrawny little white woman. You come in here tryin’ to change somethin’ you don’t know nothin’ about. You know what these slits in my eyebrow mean?” He pointed to two shaved spaces in his eyebrow. “Maybe you should be afraid of me.”
Larkin did know much of the gang liturgy and symbolism. She had learned quickly during her first year in the classroom. She had also learned not to show fear to these kids, so, although shivering inside, she calmly replied, “Mr. Parks, it appears you do not know who has the power in this room. Perhaps, you should leave us.” She moved toward the intercom.
Dupree jumped up from his desk and shouted, “Try it, bitch!”
Larkin raised an eyebrow and pushed the button. At the same moment, the literature book from beneath Dupree’s desk hit her in the face.

Re: How much truth do you put into your writing?

Don't get me started. ;-)