Research was conducted to determine what impact school organization and classroom dynamics had on student achievement. Results from standardized benchmark tests found no significant differences in scores across all schools and content areas; yet, end of course standardized measures indicated that students in sites employing block scheduling performed significantly lower in all content areas than did their counterparts in traditional settings. Findings suggested that the significant differences in student scores might be due to a dramatic loss of instructional time that was consistently observed in block classes during the last 18 minutes of the instructional period. This loss of instructional time was characterized by a dramatic increase in student behavior problems and student time-off-task.