The challenges and possibilities for improvement may vary across the three levels of an assessment system--classroom assessment, school or district assessment, and state-level accountability assessment. In this brief, the discussion of the challenges and possibilities focuses on these three levels and on two forms of assessment--formative and summative. Formative assessment, also called assessment for learning, is intended to inform teachers' instructional decisions by producing information about students' progress towards a given set of instructional goals; it allows teachers to glean information about student learning in order to adjust their instruction and/or to provide feedback. Formative assessment activities range from ongoing informal teacher-student conversations to formal teacher-created activities and instruments used at the classroom level, close to students' individual contexts. Summative assessment, also called assessment of learning, is intended to produce information about learning and academic achievement and is used for grading, evaluation, placement, certification, and accountability, among other purposes. While teachers use summative assessment to grade student learning, it is more clearly associated with large-scale, standardized mandatory tests. Measures produced by summative assessment are typically distal from students' classroom experiences, as they tend to sample broad swaths of standards.