A model of Academic Learning Time (ALT) is described, where ALT represents ongoing student learning in terms of student engagement, low student error rate, and relevance of the instructional task to the specified outcome. This model was validated in a correlational study of the relationship between these variables and student achievement in reading and mathematics. Achievement tests were administered to 139 second grade and 122 fifth grade students. ALT was measured during the inter-test period by direct observation and with records kept by teachers. These data were used to obtain student engagement rates, student error rates (low, medium, and high), and provided data on the instructional time allocated to specific content areas within reading and mathematics. Allocated time, engagement rate, and low error rate were found to be positively associated with student learning, while high error rate was negatively associated. These effects were generally consistent across both grade and content area. The set of four ALT variables accounted for an average of about 11 percent of the residual variance in achievement. These analyses provide strong support for the relationship of ALT to student learning. (Author/GDC)