MAYNARDVILLE, Tenn. — Every year, hundreds of Union County students take a field trip for the soul. Children are excused from class, loaded onto school buses with teachers and sent to a three-day Christian revival. "I am going to ask you a question," an evangelical leader recently yelled to a sea of students ready for their field trip. "If you are glad to be here, say amen!" With the ardor of a pep rally, the students shouted back: "AAAA-men!" Not everyone is so enthusiastic. Fourteen-year-old India Tracy said she was harassed and attacked by classmates for nearly three years after...