We explore how the opt-out movement has responded to the combination of a stringent federal policy with weak and often variable implementation among the states. Gaps between federal expectations and states' understandings of just how to make NCLB's demands a reality have created policy ambiguity. Parents who oppose standardized testing have recognized the resulting tensions and oversights in state education systems as a policy vacuum rife with opportunities for resistance. We examine how parents have exploited policy ambiguity through creating contested spaces--places of agency in stringent policy environments in which grassroots can question policy authority and take action. We conclude by considering whether these contested spaces are sustainable and whether the policy outcomes generated in contested spaces are reasonably equitable.