This paper discusses on the principals of school governance system related to Schools attached to national universities under the educational autonomy system For this, the materials, literatures, government reports were reviewed in terms of its original roles and tasks and the legal base(Act and its decree) of the Schools attached to national universities was analyzed as well. Through these processes, the overall development of the schools was proposed in order to enhance management efficiency and decrease government influence with highly secured self-governing power based on self-regulation and accountability. As a conclusion, for the development of its original purpose, three types of governance system were proposed. Firstly, in case of national university transforms its governance structure into one of a corporate, the school system should be changed to foundation school model as well. And, in accordance with local educational autonomy system, public school model with highly self-governing power could be considered as well. Finally, for the sake of enhancing original tasks and roles, stabilizing schools under current system was suggested in accordance with the regulations.