All successful organizations, including successful high schools, have employees who go beyond their formal job responsibilities and freely give of their time and energy to succeed. Organ was the first to use the phrase "organizational citizenship behavior" (OCB) to denote organizationally beneficial behavior of workers that was not prescribed but occurred freely to help others achieve the task at hand (Bateman & Organ, 1983). The willingness of participants to exert effort beyond the formal obligations of their positions has long been recognized as an essential component of effective organizational performance. Research on organizational citizenship behavior has produced some intriguing insights in a variety of organizational settings (Organ, 1988; Organ & Ryan, 1995), but it has been neglected in the study of schools. In an earlier paper (DiPaola & Tschannen-Moran, 2001), Organ's concept of organizational citizenship (Organ, 1988; Organ &Ryan, 1995) was developed and applied to public schools. This analysis builds on that earlier work. In this analysis, the concept of organizational citizenship behavior is reviewed and then applied to schools. A set of hypotheses linking organizational citizenship behavior with student achievement in high schools is developed and tested. A significant relationship was found between student achievement on standardized tests and the level of organizational citizenship behaviors of the faculty in the high school sample studied. The relationship remained significant even after controlling for socioeconomic status (SES). Finally, a set of suggestions for further research and a series of practical suggestions for high school administrators are provided.