He found that the key to making a difference was making teaching and learning 'visible'.Hattie explained how visible teaching involves teachers deliberately intervening to ensure changes in their students' thinking. He also set out to identify the message underlying them.

With the exception of the school, all of these six had considerable influence on student learning outcomes.But Hattie did not merely detail lists of the relative effects of the different influences on student learning.

He worked through each of these categories of influences to evaluate which specific innovations and influences were above or below the hinge point. Hattie found that the average effect size of all the interventions he studied was 0.40 and therefore decided to judge the success of innovations and influences relative to this 'hinge point'.Hattie identified six main areas that contribute to learning: the student, the home, the school, the curricula, the teacher, and teaching and learning approaches. Hattie synthesised the findings from related meta-analyses and converted them into a common measure (an effect size).He developed a way of ranking all the various influences and innovations in these meta-analyses according to their effect sizes, from those that had very positive effects to very negative effects on student achievement, creating a 'barometer of influence' which ranged from -0.20 to 1.0. Each meta-analysis had reviewed studies that gave evidence about the impact on student achievement of a particular intervention. (2009) Visible learning: A synthesis of over 800 meta-analyses related to achievement, Routledge, LondonHattie looked at more than 800 meta-analyses about influences on learning. One study set out to find out just that:Hattie, J. There is a great deal of research about what makes a difference in the classroom, but of greatest importance to teachers is knowing which teaching and learning experiences make the most difference.

Hattie research