How does grade configuration impact student achievement in elementary and middle school grades?

Recently, there has been a move towards K-8 schools as opposed to separate elementary and middle schools, especially among urban districts. In this paper, we examine the effect of enrollment in separate elementary and middle schools relative to enrollment in a K-8 school using longitudinal data from an anonymous district in the United States. The choice to enroll in a K-8 or separate elementary and middle schools is potentially endogenous. While previous research has taken steps to address the possible endogeneity when estimating the effects for separate middle schools, previous research has not addressed the possible endogeneity when examining the effect at the elementary level. Without generating an unbiased estimate during the elementary grades, we cannot fully understand the impact of policies that have shifted the grade arrangement of separate elementary and middle schools to K-8 schools. In this paper, we employ a research design that leverages the fact that the anonymous district closed several schools and rezoned their students to other schools with new boundaries. We compare students on the side of the new boundaries who are assigned to a separate middle or elementary school to students on the other side of the new boundaries who are assigned to a K-8 school. When taking into the consideration the effect at the elementary level, our results are much less supportive of a K-8 policy than previous research.