Andreas Schleicher is right to warn that educational improvement can no longer be measured by national standards that, as Roger Pope points out (“Out of control”, Comment, 16 November), are statistically manipulated. Students who meet the criteria do not necessarily get the grade because public examinations have never been truly criterion referenced. In this context it is impossible for every student and school to succeed - the success of some will be at the expense of others. We must decide whether we want a system that is designed primarily to compare student against student and school against school, or one that genuinely recognises achievement against agreed and carefully monitored learning outcomes. Schleicher shows us the way by pointing to education systems with both excellence and equity, where all students are expected and allowed to achieve high standards.

Phil Taylor, Ashbourne, Derbyshire.