I read about Visible Learning on this Connected Principal post by Johnny Bevacqua about a professional development opportunity focused on John Hatties's research. His research was used to support CEL 5 D+ and our Classromm 10 work and is one of the foundational pieces used to support instructional change today. Visible Learning is a professional develop organization focused on Hattie's research.
The info graphic below by Terry Burr for Osiris Education, the British partner of Visible Learning, captures the major findings of the research. The top 7 and bottom 7 effects are shared with a summary for why they work.