A shortage of half-pint milk cartons is affecting school meals in cafeterias across the US School officials from New York to California are scrambling for backup options after a main supplier of cartons said demand has outstripped supply The tiny, half-pint cartons of milk served with millions of school lunches nationwide may soon be scarce in some cafeterias, with districts across the country scrambling to find alternatives.The problem is not a shortage of milk itself, but the cardboard cartons used to package and serve it, according to dairy...