The scope of secondary education is now so broad, its purpose and aim are so diversified, that no one specialist can aspire to be accepted as an authority in the entire field. The content of secondary education is so diverse, methods of instruction and of administration are so varied, that no one practitioner can hope to present views acceptable to all engaged in the field. When unity of views or of practice does not exist, it is impossible to express a unified philosophy or to formulate a procedure universally valid. Under such circumstances, it seems best to prepare the prospective teacher or administrator for his work by giving him the conclusions representing the best thought and practice in this entire field. Especially is this procedure advantageous if, as in the case of this volume, the specialists writing have a broad acquaintance with present practices, intelligent views and wide sympathies in the whole field of education and also a tolerance of innovation justified by experience.