The story begins with threatening letters. In October 2014, the U.S. Department of Education reminded Colorado’s chief state school officer that the department “ha[d], in fact, withheld Title I, Part A administrative funds . . . from a number of States for failure to comply with the assessment requirements” under the Elementary and Secondary Education Act. Given the occasion, the department implied, it wouldn’t hesitate to be ruthless.

Colorado could be forgiven for assuming it was authorized to craft its own policies in this arena; according to the Wall Street Journal, the Every Student Succeeds Act (ESSA) represented “the largest devolution of federal control to the states in a quarter-century.” But what precisely had become of No Child Left Behind’s 95 percent participation requirement? In this Essay, I parse the state and federal laws at play to determine whether the federal government really has the legal authority and political will to withhold funding from states that allow students to opt out of standardized assessments. I also evaluate Colorado’s proposed response to the federal threat, gauging its conformity with the letter and the spirit of ESSA.