This yearbook is intended to be primarily a highlighting of the essential elements of those basic mathematical understandings which should be continually developed and extended throughout the entire mathematics curriculum. An attempt is also made to illustrate training in mathematical modes of thought, sometimes labeled problem solving or creative thinking. A second objective is to define and illustrate some classroom procedures and their psychological bases, which are appropriate for all levels of instruction. The third objective is to assist teachers and supervisors in extending and applying the ideas of the book in their own situations. Chapter topics include number and operations, relations and functions, proof, measurement and approximation, probability, statistics, language and symbolism, modes of thought, implications of the psychology of learning for the teaching of mathematics, and promoting the continuous growth of mathematical concepts. (MP)