The paper examines the professional training of Principals of secondary schools in Nigeria. The study observes that teaching experience appears to be the major yardstick that is being used currently to promote teachers to the rank of school Principals in the country. After drawing experiences from some other countries on how Principals are trained and appointed, the paper concludes that teaching experience should not be the only yardstick for appointing Principals of secondary schools in Nigeria. As school administrators, the principals need to be formally trained before they assume administrative positions. The paper therefore suggests that the National policy on Education should be amended such that potential principals would attend mandatory leadership courses at the National Institute for Educational Planning and Administration (NIEPA) before they assume managerial positions. It further proposed that NIEPA should expand its programmes to provide the opportunities and avenues for such training.