Hattie says ‘effect sizes’ are much the best way of answering the question ‘what has the greatest influence on student learning’.

All teaching-learning methods, which are higher than d=0.4 points bring remarkable improvement as shown in the graph.

A key condition is that the view of the teacher on his own role is crucial. It is about the specific mindset that teachers have on their role. It is crucial that the teachers know what effect they have on the learning of their students.

• Reverse effects in red are self-explanatory, and below 0.0

• Developmental effects are 0.0 to 0.15, and the improvement a child may be expected to show in a year simply through growing up, without any schooling. (These levels are determined with reference to countries with little or no schooling.)

• Teacher effects "Teachers typically can attain d=0.20 to d=0.40 growth per year—and this can be considered average" ...but subject to a lot of variation.

• Desired effects are those above d=0.40 which are attributable to the specific interventions or methods being researched.

from: http://image.slidesharecdn.com/earlipresentationbyjohnhattieforweb-120423073342-phpapp02/95/slide-9-728.jpg?cb=1335185355