Every year there are high achievers at primary school, pupils scoring in the top 10% nationally in their Key Stage 2 (KS2) tests, yet who five years later receive a set of GCSE results that place them outside the top 25% of pupils. There are about 7,000 such pupils each year, 15% of all those we term as highly able. We call these pupils our "missing talent" and in this research brief we explore who they are, their routes of study at secondary school and how we might best raise their aspirations and achievements by the age of 16. Key findings from this report include: (1) 15% of highly able pupils who score in the top 10% nationally at age 11 fail to achieve in the top 25% at GCSE; (2) Boys, and particularly pupil premium eligible boys, are most likely to be in this missing talent group; (3) Highly able pupil premium pupils achieve half a grade less than other highly able pupils, on average, with a very long tail to underachievement; and (4) Highly able pupil premium pupils are less likely to be taking GCSEs in history, geography, triple sciences or a language.