The impact of school sixth form size on educational attainment of pupils at Key Stage 5

The analysis found that whether sixth form size has an impact upon sixth form educational performance varies according to the measure of sixth form performance used i.e. A level Point Scores, A* to C grade at A level, or A* to A grade at A level.

Regression analysis found no good evidence that A level point scores were diminished or increased by larger sixth forms, over the range of sixth form size in Wales, when many controls were included. Sixth form size was defined as the total of Year 12, Year 13 and Year 14 pupils.

The same is true for three A* to C grade A level performance; when Year 12 numbers are the same as Year 13 there is no size effect on sixth form performance.

However, for three A* to A levels, a larger sixth form does appear to be beneficial over the entire size range currently observed in Wales. A pupil's chance of achieving these grades approximately doubles between sixth form sizes of around 100 (5% probability) and 500 (11% probability). The maximum sixth form size in the dataset analysed was 492 pupils, while the average sixth form size was 226 pupils. A caveat is that this achievement measure, and the three A* to C grade indicator, are considered experimental; as they are still being developed internally by the Welsh Government, and are not at present used by schools.