This article examines the extent to which adequate yearly progress (AYP) is a valid and reliable indicator of improvement in low-performing high schools. For a random subsample of 202 high schools, the authors investigate the school characteristics and the federal and state policy contexts that influence their AYP status. Logistic regression models reveal that the strongest predictors of AYP status in low-performing high schools are the number of student subgroups for which schools are accountable and their No Child Left Behind improvement status. Analysis of state report card data further paints a confusing landscape in which improving low-performing high schools are sanctioned whereas similar schools showing less improvement are not. (Contains 1 figure, 12 tables, and 3 notes.)