The paper describes the PROVE School, an alternative high school providing behavioral and academic programming using an extended school day concept for profoundly behavior disordered students in Proviso township, Maywood, Illinois. The extended day concept of crisis intervention (in which students are allowed to leave school for the day only when they demonstrate socially acceptable standards of conduct) is combined with a continuum of positive and negative consequences. Positive program components include a behavior modification point system, regular positive social reinforcement, and positive staff interaction on a one-to-one basis. Among negative approaches to programming are loss of points, time after regular school hours, and physical restraint when necessary. Program terminology is explained and includes "child finds" (to combat truancy), "late night and overnight coverage" (when students are required to remain after school hours), "activity coverage" and "good times" (reinforcing activities tailored to individual student preferences). The literature on the extended school day concept is briefly reviewed and results are given of a survey of 25 area alternative schools for the following: length of detention programs, after school programs, faculty meetings and parent meetings, and faculty compensation methods and future plans. Finally, present operational practices of the extended day programming are detailed for each of the program components. (DB)