Her senior year was just a month old at Newfield High School in Selden when Tiana Rapp, 17, opened her gym locker and discovered someone had pilfered a whopping $150 from it. Police have arrested a hall monitor, Linda Cubano, and charged her with three counts of petty larceny in connection with the thefts. Rapp said she had reported the missing money to school officials, who suspected a student was responsible. But something didn't add up, she said, because the girls' lockers were patrolled by an adult hall monitor. The criminal struck again a couple of weeks later: That time,...