Alex Weatherall
Pedro De BruyckereDid the effect of collective teaching efficacy just drop (or did John Hattie's team make a mistake?)
I'm a nerd on effect sizes and have been following the Visible Learning MetaX website for a long time. Little was I surprised to see a considerable drop in the effect size of Collective Teacher Efficacy. While in October, it still was 1.34-136, now it suddenly dropped to 1.01-1.11: Many average effect sizes in Hattie's work have been dropping because science is…
Did the effect of collective teaching efficacy just drop (or did John Hattie's team make a mistake?) *updated*
*update*: check John Hattie’s reaction under this post. It was indeed a mistake, and it will be corrected. *Not updated*: I’m writing this on November 4th, 2025, and it’s still not corrected! I’m a nerd on effect sizes and have been following the Visible Learning MetaX website for a long time. I was surprised to… Read More Did the effect of collective teaching efficacy just drop (or did John Hattie’s team make a mistake?) *updated*