You’ve done your pupil progress meetings, identified the children who need additional support to achieve their best. You’ve meticulously and rigorously analysed the data, in conjunction with teacher assessments, and created the higher ability reading intervention group, the low prior attaining maths intervention group, and the intervention group to get those children finally using complex sentences in their writing. The Teaching Assistants have been briefed, trained and your teachers have planned the activities for each group. You’ve done all you can to prepare. Come to the end of these interventions: how do you know what the impact has been? Perhaps a TA has been running it, or a teacher, or a member of SLT: our biggest (and most expensive) assets. But how do we really know that this intervention has had an impact, and does this impact outstrip the benefit they would have had having stayed in class and experienced Quality First Teaching?