The purpose of this study is to establish the objective deterioration grades and evaluation criteria of building equipment system of educational facilities available for reasonable maintenance and remodeling of them. For the purpose of it, the actual conditions of building equipment systems of the 148 buildings of 84 middle and high schools in Seoul 20 years after construction are investigated and surveyed through one-on-one interviews and questionnaires. And, deterioration grades of them are estimated by the evaluation criteria which is proposed in this study. As a result of this study, the 10 deterioration grades and the 4 evaluation criteria of the 6 performances of building equipment system, which are heating and cooling, water supply and drainage, hot water supply and electrical power performance, are suggested. And, as a result of the survey, it showed that 24% of the investigated school buildings were estimated C grade which needs partial remodelling, and 51% of the school buildings were estimated D grade which needs extensive remodelling. And, 25% of the school buildings were estimated E grade which needs overall remodelling or alteration of building equipment system.