Between 1900 and 1930 the number of school physical education programs multiplied significantly in the United States. Historians of physical education have chronicled this occurrence and offered several explanations for this growth. Their explanations have focused on the role of World War I and the attendant, military conscription, the playground or play movement, and athletic programs. However, it is somewhat surprising that historians have neglected prerequisite changes in the structure and functions of American public schools, particularly urban schools. For it was in the years between 1900 and 1930 that important changes occurred in public education, changes fueled by twin laws for compulsory schooling and against child labor. The purpose of this paper is to discuss the influence of educational reforms and the impact that these reforms had on the diffusion of physical education during the period between 1900 and 1930. The focus of this paper is to review the impact of industrialization, immigration, and urbanization on educational reforms that led to the development of the platoon school model. The platoon school was developed in Gary, Indiana in 1908 by Gary's school superintendent, William A. Wirt. It was in Gary that Wirt gradually built an innovative school system that captured national attention. Wirt devised a diverse curriculum to prepare youth for the new emerging industrial state, and a significant part of Wirt's innovative curriculum was occupied by sports, games, and play activities. Wirt referred to his system as a work-study-play school, but it was commonly referred to as a platoon school and the Gary plan. The platoon school curriculum embodied the progressive view of a social institution. It was the ideal meeting ground for the two different and somewhat contradictory groups of progressive educators: the social progressives and the administrative progressives. By 1929, the platoon school curriculum had been adopted in 1,068 schools in 202 cities located in 41 states. Clearly, future historical accounts on the making of American physical education must give ample attention to the important role played by William A. Wirt's platoon school during the period between 1900-1930. This study is based on primary sources including the Wirt Papers.