This symposium article, to which three authors contribute distinct parts, presents the rationale for standards-based language assessment and examines both the uses and misuses of language assessments in English-speaking countries that are engaged in standards-based education reform. Specifically, they focus on the assessment of emergent bilinguals (also referred to as English language learners or English as an additional language students). The first part lays out the intentions and challenges of standards-based language assessment for emergent bilinguals, focusing on validity concerns. The second part describes classroom-based teacher-led assessments of emergent bilinguals in England, which carry high stakes along with the national standardized tests. This contrasts with what is happening in the United States where, as the third part describes, the main focus is on high-stakes standardized testing for purposes of accountability. In addition to the challenges inherent in attempts to measure language in meaningful ways, a thread cutting across the authors' accounts is the widespread practice of high-stakes standardized testing. The U.S. and English cases show how issues of validity arise when emergent bilinguals are simply included into assessments intended for English monolinguals without appropriate differentiation, and when an assessment is used for purposes beyond what it was designed to do. As all of the authors of this symposium article contend, assessments--particularly when standardized--hold the potential to dominate standards-based education reform efforts when they are ultimately summative and attached to severe consequences.