John Hattie's Visible Learning research, now based on the data of 300 million students, outlines a list of influences related to learning and achievement. There are some new influences at the top of the list entries since the first Visible Learning study was published in 2009. In a recent presentation Hattie cites the new number one as “collective teacher efficacy”. That is, making teachers believe: “I cause learning". Collective efficacy is not about making teachers feel good about themselves, it is more complicated than just believing you can make a difference collectively. Hattie’s definition of “collective efficacy” is "collaborative conversation based on evidence”. Hattie states that the purpose of collective efficacy is to build teacher efficacy through collaborative conversations based on evidence collected. In summary, amongst other components, Hattie recommends we need to move away from looking at teachers teaching to sharing observations of impact and collectively evaluating this impact.

Opportunities for teachers to come together, share, and collectively evaluate impact on student learning is critical. Both Hattie and Ewan Macintosh, who highlights the importance of professional development for teachers led by teachers, highlight the power of teachers learning from each other. Forums such as TeachMeets and Symposiums provide teachers with an opportunity to share their learning, the impact on student learning, and invite colleagues to enter into conversations based on evidence.