This paper examines the impact of the teacher certification program in Indonesia in 2007 and 2008 on student and teacher outcomes. I create a rule-based instrumental variable from discontinuities arising from the assignment mechanism of teachers into certification program. The thresholds are determined empirically. The study applies a two-sample instrumental variable (TSIV) method to combine information from two different datasets. I find that there is no strong evidence of the effectiveness of certified teachers on student learning outcomes and teacher performance, as measured by student test scores, teacher test scores, teacher attendance, and teacher involvement in non-teaching side jobs. © 2017 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.