This study investigated the engagement rates of 25 students in a mixed-age classroom of third- and fourth-graders. The time on task of the students was compared using thematic, interdisciplinary instruction and traditional, single-subject instruction. Engagement rates were determined using an engagement rate observation form, students' self-perceptions, and teacher reflections. The results indicated that the students' engagement rates were higher during thematic instruction than during traditional instruction. Two appendixes contain copies of the engagement rate observation form and the student self-evaluation form. Contains 16 references. (Author/MDM)