This paper evaluates the impacts of a Grade 1 literacy intervention, Mahay Mamaky Teny (MMT) translated to “I know how to read”, implemented in Madagascar on student literacy outcomes. The intervention included teacher training and coaching on effective literacy-focused instructional routines and strategies, scripted lesson plans for teachers, and student learning materials. We employ a cluster-randomized controlled trial, at the school level, to identify the overall causal effects of the intervention on student literacy outcomes using the Early Grade Reading Assessment (EGRA) administered in the Malagasy language. We contribute to the evidence base by disentangling the effect of teacher adherence to scripted lessons from the overall effect of the intervention. We achieve this by linking classroom observation data to student reading assessment scores. Our results show that students in the intervention group outperform their control group counterparts on all EGRA subtasks including letter sound identification, syllable reading, oral reading fluency, and reading comprehension. Additionally, within the intervention group, we find that EGRA performance is significantly higher when teachers followed the scripted lessons than when teachers did not.