A key point about John Hattie’s remarkable work (“He’s not the messiah”, 14 September) is one he makes himself in Visible Learning - it is not a recipe but an explanatory story. This is an invitation for teachers to take the professor’s generalised findings about what works best and contextualise them in their classrooms through experimentation and enquiry. However, high-stakes testing too often gets in the way. As well as “growth for every student”, we need growth for every teacher. Accountability processes should encourage, not stifle, teacher growth and creative application of research evidence in the classroom.

Phil Taylor, Ashbourne, Derbyshire.