MURFREESBORO, Tenn. -- Staff members of an elementary school staged a fictitious gun attack on students during a class trip, telling them it was not a drill as the children cried and hid under tables. The mock attack Thursday night was intended as a learning experience and lasted five minutes during the weeklong trip to a state park, said Scales Elementary School Assistant Principal Don Bartch, who led the trip. "We got together and discussed what we would have done in a real situation," he said. But parents of the sixth-grade students were outraged. "The children were in that room...