This textbook is a comprehensive introduction to the assessment of students in K-12 schools who use two or more languages in their daily life: English Language Learners (ELLs), or Emergent Bilinguals. The book includes a thorough examination of the policy, history and assessment/measurement issues that educators should understand in order to best advocate for their students. The author presents a decision-making framework called PUMI (Purpose, Use, Method, Instrument) that practitioners can use to better inform assessment decisions for bilingual children. The book will be an invaluable resource in teacher preparation programs, but will also help policy-makers and educators make better decisions to support their students.