Social justice research is popular in education, but social scientists have limited emancipatory methodological procedures, especially in scale construction approaches that empower marginalized communities in defining their own lived experience. Therefore, this study develops the Transformativist Measurement Development Methodology, exemplified using the development of the peer bonds scale. The sample (167 students across two democratic school communities) was randomly selected, then purposive sampled for optimal diversity. Across Transformativist Measurement Development Methodology's six stages, mixed methods were used to check assumptions, set parameters, inductively operationalize the construct, qualitatively generate items, quantitatively examine psychometric properties, and examine trustworthiness. This work contributes to mixed methods social justice efforts that apply transformativist approaches to research processes for emancipatory social science procedures while enhancing rigor in scale construction methodology.