Schools are desperate to find ways to predict students’ progress from year to year and between key stages. Seemingly, the most common approach to solving this problem is to produce some sort of ‘flight path’. The internet is full of such misguided attempts to do the impossible. Predicting a students’ progress is a mug’s game. It can’t be done. At the level of nationally representative population sample we can estimate the likelihood of someone who is measured at performing at…