Often times the appointment of principals in Kenya is not strictly based on criteria to select those with requisite leadership training and skills .The principals, therefore, need to be taken through training programmes . Sometimes these programmes are not based on Training Needs Assessment (TNA). The low performance in examinations in Kisii County may be an indication of compromised quality education due to poorly or inadequately trained Principals. The objectives of this study were: To identify the educational supervision competencies that secondary school principals need in order to effectively perform their educational activities in their schools; and to develop a training model for the effective training of Principals in Kenya. The study used a mixed method research design and within it used concurrent triangulation. The study was done in Kisii County, which is one of the 47 counties in the country which register poor academic performance in national examinations in both primary and secondary schools. The target population was 360 principals and 11 Quality Assurance and Standard Officers (QASO). The sample population consisted of 36 principals and 9 QASOs selected through simple random sampling. Questionnaires and interview guides were used for data collection. In order to ensure the validity of the instruments, they were vetted by 3 Research Experts of Jaramogi Oginga Odinga University of Science and Technology. Test- retest method was used to ascertain the reliability of the research instruments. From the study the training needs of the principals in terms of the form of training, the duration to be taken, the institution to be in charge, timing of the training, the need for field practicum and need for induction of principals before assuming office were established. A training model for principals based on these findings is proposed. It is recommended that bodies charged with the responsibility of training principals in Kenya should consider adopting this model.