For every course, BOSTES hires a team of examiners every year. Whilst it's not uncommon for a certain person to be marking more than two years in a row, they always need to apply to do so. They also must declare if or if not they have a relative or someone they know sitting an exam.
Examiners are trained every year to ensure that how they mark will always comply to BOSTES' standards and the syllabuses.
I now take information from my English teachers in Yr 10, 12 and my physics teacher in Yr 12.
For something like English, marking is a bit more painful because a ton of examiners just sit in one big hall (potentially stuffy) and mark. There will be a small bunch of senior markers with greater experience, and they mark with a ton of other examiners. Every marker is assigned one unique question to mark.
Every section is marked twice with the exception of the comprehension. If the marks between the teachers are close, then in general the average (rounded up if necessary) is taken. If there's huge discrepancy, the senior marker will also mark the paper and make a judgment.
Due to the nature of options in which texts are studied, in general one text is examined first. This is usually a popular one (e.g. Module B - Hamlet). The way these essays get marked becomes a standard to how the essays are marked for all the other texts.
Note that the examiners are more interested in how you tackle the rubric, not your description of the plot. That way, the markers have a focus as to what needs to be marked. In this way, any teacher can mark any essay for any text.
This is also the case with virtually every single subject. The one unique exception is mathematics, which can be marked at home due to its black-and-white nature.
(Examiner and marker got juggled interchangeably, but they mean the same thing here.)
Perfect response!

some additions:
- Markers can mark electronically from their homes after they have been 'trained' by the senior markers and are marking satisfactorily, though marking centres are also common
- I
believe that teachers will also be given questions which match texts that they have knowledge of,
or that they are required to know the text to a basic level. Or perhaps given resources. Assume your marker has the knowledge of a casual movie-goer, meaning they won't need the plot, but they'll need thematic analysis
-
Beginning with the 2014 cohort, not everything is double marked. I only found this out extremely recently myself. But there are checking methods in place that will, omitting details, mean that scripts can/will be double marked in certain circumstances. Further, teachers
can be banned from marking and required to re-train if discrepancies are noticed, in which case things will be marked again. In short, don't let it worry you that things aren't double marked, because the new checking mechanisms are actually probably better in my opinion. Much harder for teachers to be consistently over/under cutting students results
