<p>In 1919, Carleton Washburne took over a superintendent of Winnetka and started reforming education system which lasted until 1943. In this article, I am attempting to explore the content of curriculum development in Winnetka public schools in 1920s through focusing on the issues as follows: First, I examine the educational philosophy of Group and Creative Activities which Washburne gradually formed throughout his Europe study tour. Second, I focus on Frances Presler’s contribution in order to analyze her role in helping teachers in developing curriculum. She was a leader of Group and Creative Activities of elementary schools.</p><p>I found the meaning of the facts of the curriculum development as follows: First, Washburne understood the importance of group activities based on Rojer Cousinet’s theory, “division of labor,” and then claimed to lead children to be aware of the importance of interdependence of the individuals with society. The awareness of interdependence was the educational fundamental principle of Group and Creative Activities. Second, Presler practiced Washburne’s principle of the project activity, which was specified as three phases as follows:</p><p>①“Development of Background,” ②“Determination of Activities,” ③“Handling the Activities”. Throughout three phases, she assumed, children would be able to experience the development of individual’s talent and group’s empowerment. As a result, individuals began to be aware of interdependence of the individuals with society. Furthermore, Presler cooperated with other advisors, helping teachers organize the project activities. In particular, they formed the themes of the project activities so that teachers could develop the units in terms of Washburne’s philosophy. Besides, they wrote Teacher’s Guide for Group and Creative Activities which presented practical guidelines including sample units, criteria, activity plans and references. Due to the advisor’s support, teachers could understand Washburne’s philosophy for developing their competences to organize the project activities in a flexible manner so that children could develop spontaneous interest and need.</p><p>Presler, thus, practiced Washburne’s principle of Group and Creative Activities in the project activities. She worked together to organize the environment for the curriculum development so that teachers could develop the curriculum independently. Washbunre, in his later years, described the educational reformation in Winnetka as “Winnetka Educational System”, in order to emphasize the importance of the cooperative relationship which enabled teachers to develop curriculum flexibly. As has been stated above, advisors took important roles in “Winnetka Educational System,” in particular Presler emphasized.</p><p>As has been discussed, the advisors especially take significant role in mediating and facilitating educational philosophy into practice.</p>