Drawing on an original data set of over 4000 teacher-union endorsements in local school board elections, I make three contributions to the literature on union power in education politics. First, despite some recent evidence that union strength has narrowed at the federal and state levels, I show that teachers’ unions remain an influential player in local school politics today. Second, I provide evidence that teachers’ unions are active and influential in elections that occur outside of traditionally strong union states and prolabor school districts. Finally, I show that union-endorsed candidates do not win simply because they are stronger candidates ex ante, but in part, because union support makes them more formidable candidates on Election Day. I conclude with a brief discussion of the implications of these findings and suggest some avenues for future research on interest groups in local school politics.