This study investigated questions concerning the incidence of student off-task activities, which interrupt learning, in different academic activities, within different activity formats (e.g., individual, group), and among students differing in achievement growth (AG). AG was defined as a pattern of continuous growth during the previous two years in the Total Reading grade-equivalent score on the Stanford Achievement Tests. Fourth grade students from four classrooms in two elementary schools in an integrated urban school district served as the sample. High- and low-AG students were identified in each classroom. Thirty observations of four target students for 30 minutes each were made in four subject areas. Student behavior, type of academic activity, off-task activity and activity format were coded on a minute-by-minute basis. Twenty different academic activities and eight activity combinations were identified and then grouped into 10 categories. Six off-task activity types were found. For each student observation, activity and format interruption rates, percent of time in each off-task activity type, and total time off task were determined. Among the significant findings, the high-AG students were more likely than low-AG students to go off task during creative activities. Low-AG students were more likely to go off task during recitation. High- and low-AG students spent nearly equal amounts of time off task. In the discussion of the results, several implications for educational practice are indicated. (Author/RH)