In this brief, we set out to understand how unionization may or may not shape practices central to charter schools' ability to serve students. The study, an exploratory one, includes 29 interviews across eight schools that unionized four to six years ago. Our results point to areas of concern, optimism, and future research. We found: (1) Unionization may help codify systems for teacher development, but it could also undermine efforts to advance teacher effectiveness; (2) Unionization may help to address pay inequities between districts and charter schools, but at the risk of financial sustainability; and (3) How unionization plays out may hinge on teachers' choice of bargaining partner and the priorities they pursue in collective bargaining.