Many states and districts are working toward developing and implementing high-quality systems that align assessments with each other, and to college and career readiness, and a comprehensive set of higher-order thinking skills. In order to support states, districts, and communities in this, the following 10 principles as guidance and common language for advancing a high-quality system of assessments are offered. The principles draw collectively on expertise developed over decades of studying and designing assessments and assessment systems, and efforts to advance the full array of college- and career-ready knowledge, skills, and behaviors for all students. They also build on existing principles for high-quality assessments and systems of assessments.