At least three states are vowing to ignore the latest requirements under the No Child Left Behind law, defying the federal government as their frustration grows over an program they say sets unrealistic benchmarks.  States like Idaho, Montana and South Dakota are fed up and preparing to reject the latest requirements for determining school progress under the 9-year-old law - even if the move may put them at risk of losing some federal funding. Kentucky is seeking a waiver to allow the state to use a different method to measure student progress. And more states could follow in seeking relief.  Many schools are far from reaching the ambitious goal of No Child Left Behind, which aims to have all students proficient in math and reading by 2014.