In fall 2017, Propel Schools initiated the expansion of one of its schools, Propel Montour. Originally a single K-8 school with two classrooms per grade, Montour added a new high school and expanded into separate elementary and middle schools over four years, adding a classroom to each grade. In this report, the authors used difference-in-difference and doubly robust regression models to examine the academic and behavioral experiences of both continuing and expansion Montour students from fall 2017 through the onset of the coronavirus disease 2019 (COVID-19) pandemic in spring 2020. The analyses did not find evidence that the academic and behavioral experiences of either the continuing or expansion students fell below what would have been expected absent expansion. Although the expansion experiences of a single charter management organization (CMO) network might be idiosyncratic to that entity and the locale and population it serves, this report should be of interest to similarly structured CMOs, the organizations from which they might seek expansion funding, those involved in school choice policy, and state and local education leaders and policymakers. [This report was supported through a subcontract with Propel Schools Foundation.]