For the past four decades, intercultural bilingual education (IBE) has been a common policy prescription to address Indigenous/non-Indigenous education gaps in Latin America. Initiatives have grown from small, localised pilots to national and state-level initiatives across thousands of schools. While there is some rigorous evidence of the effectiveness of IBE pilot initiatives at a small scale, there is very little evidence that expanding them to a larger scale benefits learners to the same extent. This article reviews the existing evidence on IBE's effectiveness and identifies a number of challenges in replicating success at scale. The authors identify factors which have limited our understanding of IBE's effectiveness, as well as factors which may have contributed to less-than-ideal outcomes for larger programmes, including uneven coverage, varying teacher quality, and limited resource availability for smaller Indigenous languages. Addressing these issues will be crucial for improving IBE programmes' ability to operate successfully at scale.