A study examined the effects of multi-age/grade instruction, compared to the traditional single-grade approach, on the reading achievement of fourth graders. Subjects, 22 fourth-graders in a single-grade class, were divided into instructional groups based on chronological age while the instructional grouping for 22 students in a combined fourth and fifth grade class at a neighboring school cut across age and grade levels. The Comprehensive Test of Basic Skills was used to measure the growth in "total reading" over a 1-year period. Results indicated no statistically significant difference between means of the two groups, although a positive mean score in favor of the multi-age instructional design was noted. (A 50-item bibliography, and the themes of study and sample lesson plans for both groups are attached.) (RS)