The Center for Evaluation Study at the University of California (Los Angeles) conducted the Test Use in Schools study to map the topography of basic-skills achievement testing and achievement test use in public schools across the United States. The survey addressed a nationwide sample of principals and teachers through a successive, random-selection procedure, and focused on determining how leadership activities impact test use. Responses were obtained from 220 principals, 475 elementary school teachers, and 363 high school teachers in 91 of the 114 districts sampled. Return rates were about 50% for high school teachers, about 60% for principals, and about 60% for elementary school teachers. Examination of the survey responses confirms that there are two tiers of student achievement assessment in the country. One tier is internal or local to the schools; it is "owned" and usually produced by the teachers themselves as tests and other assessments of achievement in the classroom by the individual student. The other tier of assessment is external to the school; it is mandated by district, state, or federal program requirements. Both tiers are underutilized; neither fulfills its potential for helping students. Case studies and research-based models are included to illustrate how schools and districts can integrate these tiers to plan for instructional improvement. There are 31 tables of study data and 6 figures illustrating the concepts discussed. A 50-item list of references is included. (SLD)