The Framework acknowledges that the new vision for science teaching and learning poses challenges for assessment and will require significant changes to current assessment approaches. The Framework emphasizes the widely shared understanding that the major components of the science education system (curriculum, instruction, teacher development, and assessment) are tightly linked and interdependent, and it advocates a standards-based system that is coherent horizontally (across classrooms at a given grade level), vertically (across levels of control and aggregation of scores, such as across schools, districts, and a state), and developmentally (across grade levels). The framework also follows an earlier report (National Research Council, 2006) in calling for a coherent system of assessments that combines multiple approaches (e.g., including both large-scale and classroom-based assessments) to meet a range of goals (e.g., formative and summative assessments of student learning, program evaluation) in an integrated and effective way.Resources and Tools:Evidence Statements: The evidence statements provide detail on what students should know and be able to do in order to satisfy each performance expectation (PE) at the end of instruction. Given that each PE is three-dimensional, the statements describe how students can use the practices, crosscutting concepts, and disciplinary core ideas together to demonstrate proficiency on the PEs by the end of instruction. The evidence statements are intended to identify clear, measurable components that, if met, fully satisfy each PE described within the NGSS. They are not meant to limit or dictate instruction and were written to allow for multiple methods and contexts of assessment, including assessing multiple related PEs together at the same time.