The Vermont Educational Quality Standards, passed in 2014, require students to graduate high school based on proficiency not merely by the accrual of course credits. The deadline to implement this policy is 2020, and thus, high schools across Vermont are feverishly revamping their systems and structures to support this change. Like many reforms, teachers are at the forefront of putting this policy into practice. The purpose of this study is to understand how teachers experience the shift to implement proficiency-based learning practices in their classrooms and how administrators support teachers in making this transition. Two Vermont high schools were selected for this study. Both were well underway with formal implementation efforts. An online questionnaire was provided to all teachers at both schools. The district curriculum coordinators and all school administrators, in addition to any instructional coaches, were interviewed on a one-on-one basis. Four teachers from each site, representing a variety of subject areas (math, science, ELA, and social studies) were also interviewed on an individual basis. Furthermore, a variety of documents were analyzed from each site, including grading policies, teacher handbooks, and other artifacts related to the implementation of proficiency-based learning. Findings suggest that teachers were actively engaged in implementation efforts within their classrooms but found the process challenging. Certain aspects of proficiency-based learning prove to be more difficult than other elements to put into practice. Engaging in a "pedagogical triage," teachers were selective with regard to which aspects of proficiency-based learning they attempted to implement. Given a lack of time and resources and the complex nature of the reform, teachers generally implemented those elements that were easier to put into practice. Furthermore, school and district administrators provided a variety of supports and resources to assist teachers' sensemaking of proficiency-based learning practices. Intentional educational infrastructure that included instructional coaches, assessment cycles, professional learning communities, and curriculum materials, were evident at both the high schools in this study. Overall, the changes teachers discussed were more evolutionary than revolutionary. This study illuminates the specific challenges with implementing proficiency-based learning in a high school setting and how teachers experience putting proficiency-based learning into practice in the classroom. Additionally, the role of instructional coaches emerged as a key element of a coherent educational infrastructure in supporting teacher sensemaking of policy messages. Proficiency-based learning holds promise as an education reform but will only work with a coordinated educational infrastructure and a timeline that allows teachers to full comprehend all aspects of the policy.