Abstract: The goal of this study was to ascertain whether Succession Planning (SP) was applied and how it impacted on the academic success of the seven secondary schools in the Catholic Archdiocese of Nairobi Kenya. The study’s objective was to examine the influence of talent attraction, leadership development, knowledge-transfer and employee retention on the academic performance of the chosen seven private secondary schools.. The Kenya Certificate of Secondary Education (KCSE) was used to evaluate the performance schools. Descriptive survey design was chosen for study. To create a sample of 104 respondents, 90 teachers were selected using simple random sampling, and two executives were chosen from each institution using a purposive sampling technique. Prior to the main study, a pilot test was done to determine how well the tools worked. Utilizing both descriptive and inferential statistics, computable data was examined. The academic achievement of the private Catholic secondary schools in the Archdiocese of Nairobi was found to be significantly correlated with teachers’ succession planning. The findings revealed that there was a significant relationship between leadership development and employee retention at a value of r=0.732 P< 0.05 and r=0.999 P <0.05 respectively. This proved that employee retention and leadership development had a greater impact on academic performance of the schools. The study recommended that the school administration needed to implement methods that are competitive to boost employee retention, uphold a positive and productive work environment, improve school structures and systems, and provide career and health benefits for their employees.