This report, based on a survey of a nationally representative sample of school districts in Common Core-adopting states, examines school districts' efforts to implement the Common Core State Standards (CCSS). The report addresses district leaders' views on the rigor of the CCSS and their impact on learning and instruction, progress on and challenges in implementing the standards, outreach efforts to inform various stakeholders about the CCSS, district collaboration with other entities on various implementation activities, and the types and helpfulness of CCSS-related assistance from the state education agency.