Educational wastage is like a canker worm that has eaten deep into the fabric of our educational system. Over the years, educational planners, school administrators and educational agencies are concerned about how to reduce this state of educational system inefficiency. This paper investigates wastage rate in some selected public secondary schools vis a viz its causes and its implications on educational planning in Nigeria with particular reference to Olorunda LGA of Osun state. Two schools were purposively sampled using rural and urban dichotomy while stratified random sampling was used to select teachers and pupils of the two sampled schools. Data for the study were collected through the use of a questionnaire titled "Wastage Rate in Public Secondary School Questionnaire (WRPSSQ)" and was administered to the teachers and the students of the two sampled schools. Findings from the study revealed that repetition was the major source of wastage in the two sampled secondary schools. The implications of this study on educational planning were made vide conclusion and recommendations in order to avert the alarming rate of wastage within the educational system. This will ascertain that the expectations of all stakeholders in turning out graduates with minimal wastage in the school system is achieved and will enable students spend only the minimum number of years expected of them for secondary education.