The Effective School Battery (ESB) is a diagnostic tool used for assessing school climate and providing a sound basis for planning and evaluating school improvement programs. This paper provides a brief look at the development of the ESB and describes its basic features. The ESB serves for diagnosing problems, opening up communication, evaluating improvement programs, and providing some indicators of a school's organizational health. Many school characteristics cited in the effective schools literature are measured by the ESB, though some characteristics unsuited to measurement are not. The ESB permits development of a comprehensive rather than a unidimensional image of the school. Among the characteristics tested are school-site leadership, use of instructional time, establishment of goals and expectations, recognition of academic achievement, parental involvement, orderliness and security of the environment, performance monitoring methods, collegiality and collaboration, staff development, teacher-student relations, student participation, the sense of community, and district support. The standard of effectiveness is extended to include character development as well as academic achievement. Practical questions about the ESB are posed and answered. Appended are samples of graphs displaying ESB findings, tables of the ESB scales and their meanings, and a three-page list of references. (PGD)