Abstract: The head teacher's mandate is no longer limited to ensuring effective learning and teaching rather, their work has become increasingly complicated with continuous management challenges. Besides new set of expectations has evolved, which makes it difficult to manage and reconcile school administration. This research sought to examine how workload in the implementation of Competency Based Curriculum, influence head teacher’s effective administration of Public Primary Schools in Nyatike Sub County, Migori County, Kenya. The study was guided by Fred Fielder’s Contingency Theory as cited by Shala, Prebreza, & Ramosaj, (2021) and adopted convergent mixed parallel design under Mixed Method Research Approach. The designs used were cross-sectional and phenomenology. The target population included 130 public primary schools, 130 head teachers, 130 Board of Management Chairpersons, 260 teachers, 4 Curriculum Support Officers and one sub-county Director of Quality Assurance Standards Officer. Both probability and non-probability sampling techniques were employed to sample the respondents for the study. Data collection instruments included questionnaires for the head teachers, BOM chairpersons and teachers, while an in-depth interview guide was employed for DQASO and CSOs. To determine reliability and validity of data collection instruments, the tools were verified using both peer review and Cronbach's Alpha. Quantitative data was analyzed using descriptive statistics with the help of SPSS version 26 while Qualitative data was analyzed using content analysis organized thematically. Findings revealed that head teacher’s workload had significantly increased thus affecting effective supervision of schools. The implementation of the new curriculum and domiciling of junior school came with challenges of increased teacher workload, inadequate retooling, inadequate infrastructure, flooded classrooms and unclear pedagogy which were significant obstacles in effective administration to the head teacher. The study recommended the need for workload balance and leadership training for head teachers, enriched retooling training programs for teachers, sufficient physical infrastructure resources through additional allocations for effective administration in the implementation of CBC. 

Keywords: Competency Based Curriculum, Implementation, Workload, Public primary schools, Head teacher’s administration