This paper aims to identify the fundamental principles on which the post modernity theory is based and to notice this in the field of Education, since this theory deals with two basic rules on which the postmodernist orientation is based, one of them denies on the absolute truth on Ontology level (related to the existence nature), and the other denies on the Objectivity and Rationality on Epistemology (related to Knowledge theory). A set of rules branch off from these two rules, which have a great effect on the educational institutions and its relationships. The relationships of the educational institutions with families and different community institutions form various areas of interferential effective operations, which represent the most effective social units, and this would be reflected on the Education and its quality.