There are hundreds of factors, teaching methods and strategies that affect student achievement. The major key for effective teaching is to know the impact of factors and strategies that contribute to student achievement.
John Hattie, one of the foremost experts on effective teaching, has amassed a database of research on the classroom factors and teaching methods that improve student learning, and quantifying the effect they have. Hattie compiled 800 meta-analyses of more than 52,000 studies of 240 million students to rank the effectiveness of different teaching practices. Hattie distils his research into a simple proposition for teachers – “know the impact”.
Hattie studied six areas that contribute to learning: the student, the home, the school, the curricula, the teacher, and teaching and learning approaches. Hattie developed a way of ranking various influences in different meta-analyses related to learning and achievement according to their effect sizes. He ranked 138 influences that are related to learning outcomes. Hattie found that the average effect size of all the interventions he studied was 0.40. Therefore he decided to judge the success of influences relative to this ‘hinge point’, in order to find an answer to the question “What works best in education?”
An effect size is a quantitative measure of the difference between two groups. Effect size calculation is based on the ‘standardised mean difference’ (SMD) between two groups in a trial, this is the difference between the average score of participants in the intervention group, and the average score of participants in the control group.