Purpose: Our study focused on identifying measurable constructs of a restorative classroom and appropriate metrics to measure those constructs through content validity analysis of a direct observation tool. The tool was designed to assess restorative practices implementation in the classroom in the context of professional development supporting teachers in a fundamental reorientation towards non-punitive discipline. Study Design/Methodology/Approach: We administered a 30-item survey to a panel of 14 experts in restorative practices implementation in schools asking them to provide quantitative and qualitative feedback on the tool's content, metrics, and utility for building teachers' skill and confidence in promoting a restorative classroom. We calculated item-level content validity indeces and scale-level content validity indeces. To interpret findings, we applied acceptability criteria recommended in the literature. We used qualitative coding to analyze qualitative responses and contextualize quantitative findings. Findings: Quantitative results indicated that the tool's structure and measures of teacher behavior were acceptable. The student behavior scale did not meet the acceptability criterion. Qualitative feedback indicated that observation and later co-reflection on teachers' use of specific restorative skills was deemed helpful to teacher implementation of restorative practices. Observations of student behaviors, however, needed to be broadened to emphasize student voice and agency and the quality of student interactions. Originality: Novel approaches to measurement are needed to facilitate teacher implementation of restorative practices as schools adopt those practices to promote equitable student agency, engagement, and belonging in a pivotal shift from existing punitive discipline systems. [This paper will be published in "Journal of Research in Innovative Teaching and Learning."]