Full Question: The table of 'effect sizes' in the book clearly identifies the effects of one element (e.g. direct instruction) and the effect size of another (d=0.82) on student achievement, but what consideration is given to the inter-correlation between those areas identified? As one example, teacher-student relationships has an effect size of d=0.72, and reducing class size an effect size of only d=0.21. However, what effect does reducing class size have on the ability for teachers to develop deeper relationships with their students?
Answer: We agree that the overlap between areas is critical. It is not as simple as combining the influences to get an increased effect. It is important to create a story about the underlying common parts such as success factors, student assessment capabilities, knowing thy impact etc.