This study investigated differences occurring in student time utilization in three teachers' classes. In Class A, the teacher used a large group instructional mode; in Class B, the teacher used a small group instructional mode; and in Class C, the teacher used an individualized instructional mode. The subjects were 60 eighth grade students from a large urban middle school. A time sampling observation system was used to record student time on task, student time off task, and sanctioned noninstructional time. Students completed a locally constructed mathematics test at the end of the study. Scores from this test were used to classify students in one of three achievement levels: high, middle, or low. Results of comparisons performed on time on task indicated that high and middle achievers spent significantly more time on task than low achievers. No difference was found between high and middle achievers. The comparisons also indicated no significant difference in time on task for any one of the three levels compared between any two of the three teachers' classes. No significant differences were found between any two achievement levels for sanctioned noninstructional time. There were three significant comparisons between achievement levels and sets of teachers' classes. The middle achievers in Class A differed from the middle achievers in Class B, the low achievers in Class A differed from the low achievers in Class B, and the low achievers in Class C differed from the low achievers in Class B. (Author/CJ)