The purpose of this study was to examine whether the use of a middle school flexible interdisciplinary block schedule would increase eighth-grade students' reading scores, as measured by the Oregon Assessment of Knowledge and Skills (OAKS). A 90-minute middle school flexible interdisciplinary block schedule served as the independent variable and was evaluated to determine its impact on student reading achievement. Extant data from the OAKS was used to assess student learning. Extant data from two groups of students were examined. The treatment group had their eighth-grade language arts and social studies classes scheduled into 90-minute flexible interdisciplinary block periods, taught by the same teacher. The comparison group had their eighth-grade language arts and social studies classes scheduled into traditional 45-minute departmentalized periods, taught by two separate teachers. The overall amount of time allocated to language arts and social studies instruction within the academic year was the same for both groups. However, the way the time was flexed and utilized within the class periods differed between the two groups. Research Question 1 addressed the possible increase in mean OAKS reading scores over time. Research Question 2 addressed the possible differences in the mean OAKS Reading Achievement Standards cut scores over time. The results of the two-year treatment condition of a FIBS for language arts instruction did not result in statistically significant results, as measured by the OAKS. The results suggest that there may not be a significant achievement difference between schools that implement an interdisciplinary scheduled compared to schools that implement a traditional, departmental approach. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]