The introduction of market-oriented standards in Uganda's education sector fundamentally transformed how public secondary schools operated and how teachers performed their duties. This study examined how market standards characterized by competition, performance-based incentives, accountability mechanisms, and privatization tendencies affected teachers' performance in public secondary schools within Masaka District. The phenomenon emerged from broader public sector reforms that emphasized efficiency, measurability, and competitive positioning of educational institutions. The study employed a descriptive cross-sectional survey design using mixed methods approaches. A sample of 239 respondents was selected from a total population of 541 stakeholders across selected public secondary schools in Masaka District. The sample comprised 214 teachers selected through simple random sampling, 8 head teachers and deputy head teachers purposively sampled, 7 district education officials randomly selected, and 10 school management committee members purposively chosen. Data were collected using structured questionnaires, interview guides, and documentary analysis. Quantitative data were analyzed using SPSS software generating descriptive statistics, while qualitative data underwent thematic content analysis. The study revealed that market standards significantly influenced teachers' performance both positively and negatively. Performance-based incentives improved motivation among 68.2% of teachers, while competitive pressures increased workload stress for 72.4% of respondents. Accountability mechanisms enhanced lesson planning (81.3%) but reduced creativity in teaching methods (64.7%). School ranking systems improved examination results by 23% over three years but diminished focus on holistic student development. Teachers' job satisfaction declined by 41% due to intensified performance monitoring. Market standards produced mixed outcomes on teachers' performance, enhancing measurable outputs while compromising intrinsic motivation and pedagogical innovation. Educational policymakers should develop balanced frameworks that integrate market efficiency principles with professional autonomy and holistic educational objectives.