The purpose of this chapter is twofold: (1) to provide a detailed review of current language assessment policies and practices with English language learner (ELL) students under the federal requirements of the No Child Left Behind Act (NCLB; 2001) and relevant research in order to evaluate their technical quality and validity, and (2) to examine the intersection of language assessment and academic content assessment in terms of their purposeful interpretation and use by educators in decision making. The authors outline a theory of action suggested by the established policies and practices of the putative ELL assessment system and critique the interpretive claims, uses, and asserted outcomes based on the available evidence. Recommendations are offered for further research that focuses on aligning and improving the disparate parts and purposes of the ELL assessment system to affect positive outcomes in ELL education.