This chapter introduces the main implications from Hattie’s earlier book, Visible Learning. However, it is important not to assume that this book is a substitute for the detailed discussion of the evidence presented in that book. Hattie wants to insure that we do not walk away with simplistic interpretations from his conclusions. For example, we might assume that any intervention with an effect size of less than 0.20 (d < 0.20) would be considered small, 0.3 to 0.6 would be medium, and more than 0.6 would be large. Instead, it would depend on the amount of resources needed for the intervention. For example, the effect of reducing class size from 25-30 students to 15-20 students is 0.22 and the effect of programs in test-taking is 0.27. Both of these fall under the category of “smallish” effects, but the latter is far cheaper to implement than the former. Because of the better return on the cost of the latter, this has a far different implication for implementation. We must go beyond the effect size in determining whether or not to implement the intervention.

Hattie also cautions the reader to be careful when interpreting overall effect sizes. He urges readers to read the accompanying dialogue and not to simply look for the practices the with highest effect sizes. For example, the overall average effect between homework and achievement is d = 0.40. But if you read the discussion carefully, you see that the effects of homework were higher for high-school students (d = .50), perhaps because they had better study habits than for elementary-school students (d = -0.08). Hattie suggests that the effect size should serve as a starting point for discussions rather than an endpoint for making decisions. Furthermore, in this example, these numbers represent how we have done homework in the past. These numbers can provide a wonderful opportunity for educators to try something different. In fact, rather than abandoning homework (because many parents judge a school by the presence of homework), some schools in New Zealand changed their approach to homework by introducing a website of “homework challenges” and evaluated the effects of this new change on student motivation and achievement. When schools evaluate the impact of what they do on student learning, this is visible learning. And that is the primary message of this book: become evaluators of your effect. Aim for a  d > 0.40 effect, and evaluate the effects of what you are doing.

The principle throughout the book is “visible teaching and learning.” When the teaching is visible the student knows what to do and how to do it. When the learning is visible the teacher knows if learning is occurring or not. Teaching and learning are visible when the learning goal is not only challenging but is explicit. Furthermore, both the teacher and the student work together to attain the goal, provide feedback, and ascertain whether the student has attained the goal. Evidence shows that the greatest effects on student learning come when not only the students become their own teachers (through self-monitoring, and self-assessment), but the teachers become learners of their own teaching (to be explained below). In successful classrooms, both the teaching and learning are visible.

A key part of successful teaching and learning has to do with the teacher’s mind frame – the teacher’s view of his or her role. It is critical that teachers see themselves as evaluators of their effects on students. Seeking interventions and actions that have positive effects on student learning (d > 0.40) should be a constant goal for teachers. Teachers should be vigilant to see what is working and what is not working in the classroom. Then teachers must use this evidence to inform their actions and their use of every possible resource (especially peers) to move students from where they are now to where the teacher thinks they should be. It is when a teacher has an appropriate mind frame combined with appropriate actions that these two work together to achieve a positive learning effect.  We need to help teachers develop a mind frame in which they see it as their primary role to evaluate their effect on learning.