The Learning Through Play at School Research Study Ukraine was a four-year longitudinal intervention study funded by the LEGO Foundation and implemented by the Australian Council for Educational Research (ACER) and the Ukrainian Educational Research Association (UERA). The study was implemented between 2019 and 2024, during COVID-19 and the full-scale invasion of Ukraine by Russian armed forces. Despite, at times, insurmountable challenges, the professional learning intervention was successful in supporting most teachers to progress from a surface level understanding of learning through play to a deep level. In addition, almost all children's literacy and social-emotional skills grew significantly from start to end of the study, and intervention school children's skills grew more than control schools. This study generated a new way of understanding how teachers develop learning through play practice and understanding at school, which could be applied in Ukraine and other contexts, for reflection and evaluation. [This report was prepared by the Australian Council for Educational Research (ACER) and the Ukrainian Educational Research Association (UERA) for the LEGO Foundation and the Ministry of Education and Science Ukraine.]