This study developed and validated a multidimensional instrument to assess teachers' perceptions and attitudes toward the reuse of treated sewage effluent (TSE) in agriculture, a key sustainability strategy in water-scarce regions such as Qatar and the wider Gulf Cooperation Council (GCC). Using factor-analytic validation procedures on data from 444 teachers, the study confirms a robust five-factor model comprising Perceived Knowledge and Awareness, Attitudes, Pedagogy, Perceived Limitations, and Sources of Knowledge, demonstrating strong psychometric properties. Beyond validation, the findings provide insight into how educators understand and engage with wastewater reuse as an educational and sustainability issue. While teachers generally demonstrate sound conceptual understanding and positive attitudes toward sustainability, persistent concerns related to health risks, food quality, and cultural acceptability reveal a notable cognitive-behavioral gap. Although respondents express strong support for student-centered pedagogical approaches, including experiential learning and technology-enhanced instruction, implementation is often constrained by limited curricular guidance, time pressures, and insufficient professional development. These findings have important implications for sustainability education policy and teacher preparation in arid contexts pursuing water resilience strategies. Recommendations include integrating TSE-related content across disciplines, expanding experiential professional development opportunities, and strengthening curricular frameworks that support applied sustainability education. The validated instrument offers a transferable model for comparable regions globally, enabling cross-cultural research and evidence-based interventions in sustainability education.