As states consider how their accountability systems will change under the Every Student Succeeds Act (ESSA), they face important decisions about which high school assessments to incorporate, what content their assessments will measure, which tests all students will take, and how rigorous those assessments will be. The purpose of this brief is to examine which English language arts (ELA)/literacy, mathematics, and science assessments states are using to measure high school students' achievement within each state's accountability system and what specific content or grades have been assessed.