Research on education politics often uses interest group pressure to explain the policy influence of teachers’ organizations. While acknowledging the power teachers’ unions have to articulate interests and shape labor policy, we explore how a less-studied variable–expertise (or the credibility of the claims they make to expertise)– shapes the policy process. In many low-and middle-income countries, teacher organizations struggle to demonstrate policy expertise and professional competence in core areas related to teaching and learning. Focusing on Indonesia from 2005-2020, we examine how the largest teachers’ organization influenced labor policy but was marginal in debates about professional standards, training, and evaluation due to its limited technical capacity and struggles to propose viable policy alternatives. Expertise is a critical policy input, and it deserves more attention in the education politics subfield. It is central for setting the agenda for policies to improve the quality of education and it has normative value for improving policy design overall.