AWINO JACKLINE ADHIAMBO2026-04-012026-04-012025-09https://repository.tangaza.ac.ke/handle/123456789/1579This study examined the influence of principals’ instructional supervision strategies on students’ academic achievement in public secondary schools in Gatanga Sub-County, Muranga County, Kenya. The study was guided by the following objectives: to determine the extent to which principals’ classroom observation influences students’ academic achievement; to examine the influence of principals’ provision of instructional materials to teachers on students’ academic achievement; and to find out the influence of principal-teacher collaborative planning on students’ academic achievement in public secondary schools in Gatanga Sub-County, Muranga County, Kenya. The study was guided by Total Quality Management Theory (TQM), developed in the 1920s by Deming. This study employed a convergent parallel mixed-methods research design. The target population was 48 public secondary schools, 48 principals, 380 teachers, and one Sub-County Director of Education. Criterion purposive sampling was used to include the sub county director of education and 10 out of 48 principals. The study used stratified and simple random sampling to select 260 out of 380 teachers to participate in the study. Questionnaires were used to collect quantitative data from teachers, and interview guides were used to collect qualitative data from sub county directors of education and principals. Cronbach’s alpha was used to test the reliability of Likert scale tools, and the coefficient of 0.83 was realized. Descriptive statistics with the help of SPSS version 25 was used to analyze quantitative data, which was presented in frequencies, percentages, graphs, and tables. Qualitative data was analyzed using a thematic approach and presented in the form of narratives and direct quotations. The study revealed that principals’ instructional supervision strategies such as classroom observation, provision of instructional materials, and principal-teacher collaborative planning influence students’ academic achievement in public secondary schools. Feedback from principals’ classroom observations was found not to be effective in improving teachers’ lesson presentations and management. Principals do not effectively observe teachers’ mastery of content, syllabus coverage, and lesson notes to enhance student performance. Instructional materials provided, such as worksheets, charts, and graphs, are often outdated, which negatively impacts student performance. The study recommended that principals should provide more detailed, actionable feedback targeting specific areas for improvement in teaching methods, lesson presentations, and class management. The government should implement policies mandating comprehensive training programs for principals, focusing on effective classroom observation and feedback techniques. These programs should emphasize developing skills for providing constructive feedback and assessing teachers' mastery of content. The government should also ensure adequate funding for the regular updating and acquisition of relevant instructional resources and create a framework for principals to assess and address the specific material needs of their schools to enhance student achievement.enThesis