A northeast Iowa high school canceled its Homecoming Dance Saturday night after a student was killed in a traffic accident that afternoon. 17-year-old Carrie Matthias of Sumner was killed when the car she was driving went out of control, crashed and rolled into a ditch about 2 P.M. in Bremer County. Matthias was thrown from the vehicle. She was a student at Waspsie Valley High School in Fairbank.