In July 1986, the Portland (Oregon) Public Schools began a 3-year study of the use of evaluative data in instructional planning and decision making in schools. This report summarizes the second year of the investigation, in which case studies of evaluative data use were conducted in one elementary school (kindergarten through grade 5) and one middle school (grades 6 through 8) in the Portland district. In the fall of 1987, the enrollment of the elementary school was 450 students and that of the middle school was 550 students. The case studies collected and analyzed ethnographic data on the use of formal tests and informal classroom assessments. Interviews and surveys with 239 teachers and 35 principals provided information on the wide range of evaluative data sources used in instructional planning and decision making. Study findings provide the basis for a Teacher Support Guide and technical support materials on the effective use of assessment information being developed in 1988-89. More evidence of data use was found than anticipated. A key factor in the use of evaluative data was the principal's attitude about and comfort with the data. Questions remain about whether the behaviors of principals and teachers in schools with high use of data are observably different from those with lower data use in schools. Further study of these questions will enhance the development of the assessment guide. Eight tables and three figures give study findings. Appendices A, B, and C present the case study survey, a summary of frequency tables, and the case study interview protocol, respectively. (SLD)