Following a high-quality early care and pre-K experience, the kindergarten-through-third-grade years set the foundation upon which future learning builds; and strengthening this continuum creates opportunities for later success. Key components of a quality experience in K-3 include school readiness and transitions, kindergarten requirements, educator quality, prevention, intervention and assessments, and social and emotional learning and mental health. Education Commission of the States researched the policies and regulations that guide these key components in all 50 states to provide this comprehensive resource and many others. The data in this document show that at least 37 states plus the District of Columbia require assessments outside of federally required third-grade assessments. Additionally, states require a range of assessments across grades K-3, including screeners, diagnostic assessments, formative assessments and summative assessments.