The classroom environment is a working surround in which children, through participating in organized experiences, can grow and develop in an optimum manner. Classroom design requires organization of principles of environmental control in order to assure efficient and successful performance. This control cannot be left to chance. In considering the nature of the human organism, how it regulates and maintains its body temperature, as well as those changes which occur under various forms of activity, three factors are relevant to design and control of the thermal environment of classrooms--(1) the developing child differs from the adult and needs a different set of standards for controlling his thermal environment in the school, (2) thermally induced stresses can alter the growth, development, and learning of children, and (3) the child's problem-solving capacity is affected by the effective temperature of his classroom. If we are to meet the needs of our growing children, then this understanding necessary for proper classroom design must include knowledge of the control of heat, air movement, and humidity along with that of light, sound, structural materials, teaching space, and the other areas that enter into making adequate classrooms in our schools. (Footnote references are given). (KK)