On a recent afternoon, Michelle Rhee, the chancellor of the District of Columbia Public Schools, came out of a meeting to find an e-mail on her BlackBerry describing a problem at Anacostia High School. Two students had gotten into a fight while being dismissed from the cafeteria. A short time later, another student, who was smoking in a stairwell, started a small fire with his cigarette. It set off the fire alarm.
While the school evacuated to the football field, a third student ran down the hall jabbing his penknife into three kids, randomly.
"You know high school kids: When something happens it sort of causes a [chain reaction]," Ms. Rhee tells me, sounding …