Florida GOP Sen. Marco Rubio wrote [1] to Department of Education Secretary Arne Duncan on Tuesday, criticizing an Obama administration plan to grant No Child Left Behind waivers to states that adopt national standards backed by the administration, the Daily Caller reports. “I am concerned,” Rubio’s letter says, “that the administration’s requirements for granting a waiver from NCLB would entail states having to adopt a federally-approved ‘college and career ready’ curriculum: either the national Common Core standards, or another federally-approved equivalent.”