Four studies conducted on junior and senior high schools which have used some form of modular scheduling suggest that a proper way to evaluate flexible scheduling includes observation of behavior, the measurement of attitudes and opinions, and assessment of pupil achievement. The studies reported were conducted on the Fresno Unified School District in California, the LaDue high school in Missouri, and the Delevan-Darien High School in Delevan, Wisconsin. The fourth study was conducted on a high school by Gerald P. Speckhard. It is concluded that (1) observable behavior can be evaluated by recording patterns of classroom activity; (2) student, teacher, and parental views of flexible scheduling can be assessed via opinionnaires; (3) the relative effectiveness of independent study, large group instruction, and small group activity can be evaluated through the use of opinionnaires; and (4) teaching effectiveness can be determined through comparative achievement testing. (HW)