... how does it manage the numbers in each class for GCSE options?
For example, if it has 180 students (6 classes of 30) but only 20 want to do Art or Music, would they still arrange them as 6 classes (e.g. 20, 20, 35, 35, 35, 35), or would they increase the number of classes to 7 in order to keep all the group sizes below 30 (e.g. 20, 20, 28, 28, 28, 28, 28).
Presumably the first option would be unpopular with everyone, but the second option would have a big impact on school budgets as it would need an extra teacher.