There is substantial emphasis on improving classroom practices, primarily through activity-based instruction, to increase the productivity of schooling. We study a large programme that seeks to promote mathematics learning in government primary schools in India. Through a cluster-randomised trial, we find that the programme increased activity-based instruction but yielded only muted impacts on learning. We provide a potential explanation: School value-added models suggest a negative relationship between activity-based instruction and test score gains. Our findings are robust to adding a community-engagement component to the intervention. These results highlight the limitations of activity-based instruction programmes for increasing school productivity.