The PLAN Student Observation Scale (PLAN-SOS) was developed to measure the percentage of time that students spend performing various behaviors judged to be important to the learning process in the system of individualized instruction upon which Project PLAN is based. An earlier document reported the use of this instrument in comparing PLAN students with students in other instructional systems. This document reports its use and adaptation in comparing various groupings within the set of PLAN classes--groupings based on grade-level, teacher experience in writing PLAN curriculum materials, and instructional organization (team vs. self-contained). The 20 categories of student behavior included in PLAN-SOS are clustered into seven groups which correspond to major emphases of the teacher training program, thus enabling the instrument to provide feedback directly relevant to the training and development of PLAN teachers. According to a systematic procedure of observation and analysis, paired and carefully trained observers (one focusing on students, the other on teachers) collected data in each of the classrooms under study. Results revealed no significant differences between PLAN groups in terms of the variety and kinds of activities engaged in and considered essential characteristics of the process of individualized instruction. (Also included are differences revealed by the instrument, although not at the statistically significant level, and an outline of the observer training program.) (JES)