With increasing globalization and mobility across countries, student populations in urban schools include various groups of language learners, including immigrant children, indigenous language-speaking students, and second- or third-generation children who enter the school with fluent oral proficiency but with limited literacy skills in a language used as the medium of instruction at school. This course is designed for graduate students who wish to develop competencies in assessing additional language learners' language proficiency in K-12 curriculum learning contexts. The use of assessment is the central theme. We will consider theoretical bases and empirical evidence that educators and teachers should know in using assessment of school-aged language learners. Various cognitive and non-cognitive factors that influence students' language proficiency development will be examined. We will examine validity, reliability, and fairness issues arising from the use of standardized tests as well as classroom assessment.