Documented and evaluated in this report is the minischool approach used by the Advancement School to improve the quality of education in two Philadelphia School District junior high schools. Background information and the history of each school is provided to put into perspective the factors dealt with in this extension program. Considerable attention is given to the development of relationships between the administrative teams of the Advancement School and each of the two schools. Specific topics covered are: the instructional programs developed at each school; team functioning; and the effects of the minischools on the students. Problems in the junior high schools of Philadelphia in general, such as discipline and teaching approaches, are analyzed. The role of the Advancement School as an external change agent in dealing with these problems is discussed. In addition, the minischool program as one approach to change in junior high schools is examined. Appendices present data collected and a listing of additional literature on the Advancement School's external program. (EB)