This study examines the supply-side decision to participate in interdistrict school choice by incorporating a district's own characteristics, those of its neighbors and a strategic component based on neighboring districts' decisions. A spatial Durbin probit model is applied to data from Massachusetts and estimates of direct, indirect, and total effects are found. Results indicate that local capacity and average test scores affect a district's own decision to participate. Furthermore, local socioeconomic characteristics, test scores and a district's own decision influences neighboring district participation. Policy implications include consideration of increases in interdistrict tuition and changes in state aid for economically disadvantaged choice students.