What does all of Hattie's research mean?

 These are the ‘Big Five’ findings that follow from ‘Know thy Impact’:

• All interventions are likely to work: the question thus should be what is the magnitude of any intervention? Any intervention higher than the average effect (d = 0.40) is worth implementing.

• The power of moving from what students know now towards success criteria: the more students are aware, as they start a series of lessons, what success is expected to look like, then the more engaged they are in the challenge and they more they are likely to enhance their achievements.

• Errors are the essence of learning and they are to be welcomed as opportunities: we go to lessons because we ‘do not know’ and thus errors, mistakes and not knowing are the key to all subsequent learning. Errors should be seen as opportunities to learn but to admit error requires high levels of trust (between student and teacher, and between student and student).

• Feedback to teachers about their impact: the most powerful person in most classrooms who relates to enhanced achievement is the teacher – the more teachers are open and seek feedback about their impact (relating to how many students they affect, which aspects of the lessons are being learnt, struggled with, and so on, where to go next).

• The need for passion about, and to promote the language of learning: it requires a passion to see the impact of one’s teaching to maintain the energies, the mission and the attentions to student learning. It also requires a narrative about effort, learning, high expectations and avoiding a language of labels, ability and low expectations.

Hattie did not merely detail lists of the relative effects of the different influences on student learning. He also set out to identify the message underlying them. 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. This requires teachers to be clear about the learning intentions, know when each student is successful in attaining those learning intentions, have knowledge of the students' understanding, and provide a progressive development of challenging experiences and opportunities for students to develop learning strategies based on surface and deep levels of learning. It also requires teachers to use feedback from students that reveals what they know and understand; to provide direction, but also step back when they see learners are progressing towards success criteria. 
What learners do is important too. When learning is visible, students are active; they are involved in determining success criteria, setting higher expectations, being open to different ways of acquiring knowledge and problem-solving.