This paper presents some initial lessons learned about the use of classroom observation data as a key form of evidence regarding improved teaching quality in a multi-year teacher development study series. This study series, commissioned by the Australian Government’s Department of Foreign Affairs and Trade (DFAT), involves the investigation of teacher development initiatives that are primarily designed to support the implementation of new primary curriculum in Lao People’s Democratic Republic (Laos), Timor-Leste and Vanuatu. The overall aim of the study series is to understand the extent to which the Australian investment has improved teaching quality and student learning. This paper discusses the processes used to design, implement, analyse and report classroom observation data in the Laos study, and key lessons learned about these that could be applied to other contexts and programs.