We analyzed the effect of grade span configurations (i.e., 6-8 versus K-8) on reading and math performance in Texas public schools for the last 5 school years. Participants in this study were 628 Texas schools (i.e., 314 middle schools and 314 K-8 schools) distributed across the 5 school years examined. Schools configured as K-8 schools were matched to middle schools using a rigorous distance-based formula. All 15 reading comparisons (i.e., grade level by school year) yielded statistically significant results, with effect sizes ranging from small to large. Eleven of the 15 math comparisons yielded statistically significant results, with all of the effect sizes being small. Regardless of student grade level or school year examined, students who were enrolled in K-8 schools had higher average passing rates on the TAKS Reading and Math assessments than did students enrolled in middle schools. Implications of our findings are discussed.