Candidates taking a reformed (decoupled) Advanced (A) level may follow an 'Advanced Subsidiary (AS) + A level' route in that subject, taking the decoupled AS level, usually in Year 12, followed by the A level, usually in Year 13. Alternatively, they may follow an 'A level only' route. The research described in this report explored whether there were differences in the A level grades achieved by 'AS + A level' and 'A level only' candidates in summer 2017. The question is of interest because summer 2017 was the first time reformed A levels were assessed, and the first time that large numbers of A level candidates had followed different routes.