This article presents initial findings from an empirical study of the effectiveness of mathematics teaching (EMT). The article explores the teaching of mathematics in two very different contexts: England and China. Within each country, the target cohort of pupils were those aged 9-10 and overall, 19 teachers, 10 from England and nine from China, participated in the study together with their pupils (n = 562). Two internationally validated instruments were used to collect the data and teacher behaviours were also measured systematically. In addition, structured observation was undertaken in classrooms in both countries. The results show that, on average, Chinese teachers scored higher on effective teaching measures and Chinese pupils outscored their English peers in the tests that were part of the study. This research project is currently collecting qualitative data but its findings, to date, reinforce the findings from previous research studies suggesting that certain teacher behaviours and classroom factors work effectively to improve student learning outcomes.