Twenty-seven second-grade students were observed during two reading periods to examine the nature of instruction and academic responding time for students in high, middle, and low reading groups. Across all groups, it was found that students spent about 20 minutes of a 120-minute typical reading period actively engaged in academic responding, and only about 2 minutes reading aloud and 8 minutes reading silently. Comparisons between high, middle, and low reading groups revealed that, in most respects, reading groups were more similar than they were different in instructional and student responding variables. Findings related to the breakdown of time in a typical reading period and variability among students also are presented. The importance of time engaged in reading as a crucial instructional variable contributing to students' achievement differences in reading is discussed. (Author)