They had to evacuate the grade school on Tuesday. Kids were getting headaches and eye irritations, tasting metal in their mouths. A teacher rolled on the floor and spoke foreign languages. No one knew what was wrong. Investigators said it could be the ventilating system, the paint or varnish, the foam insulation, the electrical insulation, the cafeteria food, the rays emitted by microcomputers, the asbestos fireproofing, the adhesive on shipping containers, the fumes from the chlorinated pool, or perhaps something deeper, finer-grained, more closely woven into the basic state of things.