KIROJoshua Shirley is curious for all the wrong reasons.Joshua Ray Shirley, an 18-year-old student at Tacoma’s Spanaway Lake High School, was sitting in band class a little before 11 a.m. yesterday morning when he took out a pocket knife. Without warning, without saying a word, Shirley plunged the knife into another boy’s head and neck.The victim was taken to the hospital with non-life-threatening injuries. And when cops arrested Shirley, he gave no motive, other than to say that “he just wanted to know what it felt like to stab somebody.”Spanaway Lake evacuated and students were sent home for the day. Shirley, meanwhile, has been booked on a charge of first-degree assault and is being held on $150,000 bail. There’s still no word on any ulterior motives, but you can be assured that’s the last time Pierce County schools makes Norman Mailer required reading.