John Hattie's research on visible learning is a comprehensive analysis of what works best in education. He conducted a meta-analysis of over 800 meta-analyses, encompassing more than 50,000 studies and 240 million students, to identify the factors that significantly impact student achievement.  John Hattie introduced the concept of effect size to measure the impact of various influences on student learning. An effect size of 0.4 is considered to be the "hinge point" for significant impact.

The term "visible learning" refers to the practices where the impact of teaching is visible to both the teacher and the students. It emphasizes the importance of teachers seeing learning through the eyes of their students and students understanding their own learning processes.