Instructional management focuses on planning, execution and evaluation of learning experiences. For teachers in pre-secondary schools to plan, execute and evaluate learning experiences effectively, they need to have good understanding of the process of cognitive development in children. Piaget has postulated that children progress through a series of four stages beginning with rudimentary reflex responses and achieving full maturity with the attainment of formal deductive reasoning. Piaget's theory also postulates that a child is an active investigator who acts upon his environment with reflex responses during infancy and then with more complex responses that emerge from early interactions. Piaget views interaction as a two-way process, one of which is accommodation and the other is assimilation. In accommodation the child's knowledge of the environment is modified to incorporate new experiences which are adaptive to the broad aspect of cognitive demands imposed by the environment. In assimilation, the child incorporates new experiences into an existing structure. Accommodation and assimilation are reciprocal and their interaction generates cognitive growth. Understanding and application of Piaget's Theory is important in the effective enhancement of teaching and learning process at pre-secondary school level. Consequently, teacher trainers, trainee teachers and practicing teachers need to keep abreast of Piaget's theory of intellectual development.