Following the passage of No Child Left Behind, there has been increased attention among researchers, policymakers, and practitioners on the emergence and implementation of standards-based education. Existing literature documents both the promise of standards-based education and the various potential obstacles to achieving success that teachers, administrators, and policymakers confront. The present study examines the early implementation process of proficiency-based education standards in the state of Maine, per Maine law "LD 1422: An Act to Prepare Maine People for the Future Economy." Under LD 1422, all schools are expected to establish a proficiency-based diploma system by 2018. Using a two-phase, qualitative approach, our findings suggest that benefits include improved student engagement, greater attention to development of robust interventions systems and more deliberate collective and collaborative professional work. In addition, practitioners and leaders indicated the need for continued work and resources to address challenges of implementation, including common working definitions, public support, time for professional collaboration, development of effective learning management system and addressing the needs of students at various developmental stages. The following are appended: (1) LD 1422; (2) Case Study Schools & School Districts; and (3) Implementation Survey. [For "Implementation of a Proficiency-Based Diploma System in Maine: Phase II--District Level Analysis," see ED561263. This study was funded by the Maine State Legislature, and the University of Maine System.]