Disparities in public boarding secondary schools are attributed to unique school’s cultures adopted by each school that affects and guides behaviours of the entire school population positively or negatively. A culture helps members to understand the environment and determine how to respond to the values, beliefs, and norms of the organization manifested by artifacts, collegiality, norms, ceremonies, and rituals. The purpose of this study was to establish implication of school culture on students’ academic performance in public boarding secondary schools in Kisii Central Sub County. The study objectives were to; Establish implication of school cultural norms and Determine implication of ceremonies on students’ academic performance. The study employed a structuralfunctionalist approach to Organizational Culture rooted by Malinowski, Radcliffe-Brown, Parsons, and Schein. Related literature was reviewed in line with the research objectives and guided by research questions. Concurrent Nested design employing Mixed Method Approach was adopted and utilized for this study. This study was conducted in Kisii Central Sub County in public boarding secondary schools. The target population was made up of 7 principals, 49 HODs, 80 class teachers, 164 student leaders, 7 BOM chairpersons and 7 PA chair persons. Saturated sampling was used to obtain a sample population constituting; 6 Principals, 42 HODs, 72 class teachers, 144 student leaders, 6 BOM chairpersons and 6 PA chair persons. Data collection instruments were Questionnaires, Interviews schedules, FGDs, Document analysis and Observation protocol. Reliability was addressed through piloting in 1 school which was randomly sampled from the target schools and test- retest was employed together with McMillan and Schumacher strategies to establish reliability and validity. Validity of instruments was further enhanced through expert vetting by two supervisors. Descriptive statistics such as frequencies and percentages was used to describe and summarize quantitative data in form of tables to show trends. Thematic analysis was used to analyze qualitative data and focused on the discussion of the themes and sub-themes as they emerged. The findings of the study may benefit researchers, principals, MOEST officers as it would be a source of knowledge on the implication of school culture on students’ academic performance. The study establishes that school ceremonies should be vetted and those that work for the school’s attainment or promotion of school’s core function should be promoted while those that are retrogressive should be in consultation explained to the stakeholders and persuaded to embrace the decisions of avoiding them.. The study suggested further study on implication of school culture on students’ academic performance in private schools or any other contexts and settings to establish if the findings of this study are robust for generalization and adoption.