The need for performance-based management in Kenya has brought in itself changes in the approach of management of institutions. Strategic planning is very crucial in realization of this important management outlook. The purpose of this study was to establish availability and the level of implementation of strategic plans in schools in Nandi County. The study adopted a mixed-method design. The target population included district education officials, senior teachers, and principals of secondary schools. A sample of 322 respondents which form 16% of the population arrived at using Krejcie and Morgan Formula was used. The study sample comprised of 85 secondary school principals out of a population of 152 and 234 senior teachers out of 1,900, and all the 5 district education officers. The respondents were selected using purposive, proportionate, and simple random sampling technique, and the instruments for data collection were questionnaires and interview schedule. Data were analyzed using descriptive statistics such as measures of central tendencies. The findings of this study revealed that majority of the secondary schools in Nandi County had no functional strategic plans to guide their respective schools to achieve their desired mission and vision; most of the plans in place are used in academic purposes, planning, and infrastructure development. The study recommends that the Ministry of Education should train well all school managers in public secondary schools on strategic planning process. The study therefore amplifies the need for the government to streamline the strategic plan policy in view of expectations of Ministry of Education circular in strategic planning of 2003.