Rethinking Hattie´s list of student achievement: Meaningful effects from standardized meta-analyses

Hattie (2009) synthesized 800 meta-analyses on 136 effects on student achievement and ranked them based on effect size.

The potential of this work cannot be overstated; finally educators could learn what improves achievement in a simple way. Unfortunately, Hattie’s approach is severely flawed. It combines and ranks existing meta-analyses never intended to be compared. They differ in several ways (e.g., calculation of effects), making the ranking invalid.

Further, because the effect sizes are calculated from different outcomes, the same effect may correspond to a practically meaningful effect (a year in school) or a trivial one (a few points on a test). In 2018, the list had grown to 252 effects, painting a crude and misleading picture of the literature.

We will develop a new type of standardized meta-analysis that allows comparisons of evidence and practical relevance within well-defined areas of student achievement (e.g., reading), and use it to recode Hattie’s list.

For each effect, we will determine the relevance for Swedish schools (expected 100), check the quality of the coding, and transfer the effects of high quality (expected 20) to an interactive platform where researchers and educators can get a nuanced overview of the literature.

For the remaining relevant effects, we will conduct three new meta-analyses, and launch a crowd-sourced international collaboration. Our goal is to give educators tools helping them make informed decisions on improving student achievement.