Between 2012 and 2016, the Learning Metrics Task Force (LMTF) laid out an ambitious agenda for nations and the international community on how to define and measure learning in the context of the United Nations Sustainable Development Goals (SDGs). This report describes the process undertaken by a group of 15 "Learning Champions"--countries, provinces, and cities--that came together to experiment with the LMTF 1.0 recommendations and develop strategies for improving their education systems. They did this by seeking to measure learning across the seven learning domains and seven measurement areas captured in the LMTF 1.0 recommendations. This report describes these domains and measurement areas along with the structure of the Learning Champions initiative and presents the experiences and activities of the 15 Learning Champions. The report shares the lessons learned from the initiative and presents examples of the tools developed through it. The report is intended to be more than just a record of an interesting experiment in educational assessment and policy. It offers valuable insights and pertinent direction to education systems and their partners alike. The aim is for countries and other education jurisdictions to perceive concrete ideas and motivation for using their assessment systems to pursue their comprehensive education goals and make improvements. Education partners, both national and international, can use this information to support education systems in installing and using holistic learning assessment strategies and mechanisms.