A staffer assigned to quell violence at a Philadelphia high school was knocked unconscious in what one union official called the worst assault since a Germantown High School teacher's neck was broken in 2007 by a student. Alphonso Stevens, known as a conflict-resolution specialist, suffered a fractured skull, concussion, and other injuries. The incident happened Friday when students were changing classes at Bartram High School. A 17-year-old student got into a verbal exchange with Stevens then grabbed him by the arm "and pushed him into the wall," said Raven Hill, a district spokeswoman. Stevens fell to the floor, unconscious. He...