The development of a project to assess the effectiveness of schools in a large urban school district is described in this paper, with a focus on improving the validity of school effectiveness instruments. Purposes of the project were to develop a methodology for reporting effective school strategies and to generate a broader profile of schools' strengths and weaknesses. The steps taken to develop the instrument included: (1) the formation of a steering committee, which conducted a literature review and identified 11 characteristics of effective schools; (2) the development of surveys based on those characteristics; (3) a pilot test and revision of parent, teacher, and student instruments; and (4) a more extensive study, which analyzed 1,474 teacher, 5,889 parent, and 8,397 student instruments. A Spanish version was also pilot tested. An outcome was that 60 schools chose to use the instruments as a primary data source for strategic planning. Two tables present the results of the questionnaire data analysis. (LMI)