A first-grader in Arlington tried to moon his teacher. Another threw chairs and destroyed the classroom. A kindergartner in Fort Worth tried to poison the classroom ferrets by feeding them crayons and glue. The child also bit other students. As most North Texas students -- including those in Fort Worth and Arlington -- return to classes Monday, teachers expect to see a continuation of a disturbing trend: It's the tiniest students who are hitting, spitting, kicking, biting and cursing like sailors. "We fight before we learn to negotiate," said Michael Parker, who oversees psychological services for Fort Worth schools. "Kids...