Student learning outcomes are an important source of evidence regarding improved teaching quality. A multi-year teacher development study series was commissioned by the Australian Government’s Department of Foreign Affairs and Trade (DFAT) to investigate teacher development initiatives 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 outlines the different approaches to sourcing and using data in each country context, and then presents initial insights about the challenges associated with the limited availability of data for measuring and reporting student learning outcomes, as a measure of teacher effectiveness. It presents key lessons learned about conducting research with limited existing student learning outcomes data and offers some solutions to inform programs in other contexts.