<p>As is well known, the progressive education movement stimulated various educators to reform school education in the United States from the late 19^th to the 20^th. Previous studies have shown that the “administrative progressives” won this struggle of school reforms, and they reconstructed the organization and curriculum of American schools in a form that has lasted to the present day. It means that since the competent administrators controlled a whole school organization effectively by a top-down approach, school reforms progressed promptly and radically. These studies investigated mainly two types of documents, on the one hand, administrative documents which were made by school boards and superintends, on the other hand, the course of studies, timetables, textbooks which were made by classroom teachers and principals. However, they overlooked “teachers’ intention” that directed practices. It is necessary to examine what teachers thought and how they design the school curriculum to uncover the actual situation of progressive school reforms.</p><p>This paper aims to reexamine the actual situation the organizational culture inside the progressive school by a case study of Winnetka Plan, that is recognized as a typical example of the “administrative progressive.” Winnetka plan was originated in 1919 by the superintendent of Winnetka public schools, Carleton W. Washburne.</p><p>The findings are as follows. Because of the necessity to conceptualize and verbalize Washburne’s educational ideal to share with teachers, Washburne learned the pedagogical concepts, particularly “the social individual,” from theories of John Dewey through the discussion with Flora J. Cooke, who was the principal of the Francis W. Parker School and an old friend of Dewey. Washburne established his educational philosophy of the Winnetka Plan, which is centered on “social consciousness,” in the mid-1920s. At the same time, highly experienced teachers (called “advisors”) of the Winnetka public schools strongly felt the necessity of socializing the colleagues as well as children. Teachers then recognized the needs of socializing school itself, including parents and children.</p><p>As has been discussed, the organizational culture in Winnetka public schools was different from the topdown system. Each Winnetka school teachers including advisors realized own role for school reforms throughout cooperation with each other, instead of subordinating to Washburne. They understood Washburne’s ideas flexibly in connection with own role. As this case study of Winnetka plan implies, we should reconsider the label of “administrative progressive,” and reexamine actual culture of school organizations.</p>