The research described in this paper was designed to assess how evaluative data were used in instructional decision making in the Portland (Oregon) Public Schools. Using the Level of Use of an Innovation (LoU) interview, a component of the Concerns-Based Adoption Model (CBAM), along with data from the Portland Achievement Levels Test (PALT), the study assessed the relationship between evaluation use and student achievement, the correlation between high-achieving schools and the frequency and effectiveness of evaluations, and the factors of evaluation that link it with improved school achievement. Thirty-six principals and 82 teachers in grades 3-8 were randomly selected for interview by 9 certified LoU interviewers. The interviews focused on four key components of the use of PALT evaluative data: (1) the use of student achievement reports; (2) the use of school administrative reports; (3) the role of evaluation reports in decision making; and (4) the decision situations where evaluation reports are used. Results are reported and tabulated for each of the four research questions. The use of evaluation was found to have a significant effect on 93 percent of the 126 teachers and administrators interviewed; these findings suggest that inservice support is needed to develop knowledge and skills in evaluation use, that personality traits may be a factor in movement of individuals to higher levels of use, and that the Level of Use interview technique produces rich descriptive information on how individuals use evaluative data in instructional planning and decision making. A bibliography is included and instrumentation is appended. (TE)