I was Dux of King’s College back in 2012 (and first each year at school) and studied this quite closely while in high school.

King’s College uses frequent internal assessment to rank students each term.

There are two types of assessments:

1. Term Orders - grades obtained by students in each subject throughout internal assessment across homework, class tests and other material (Term 1, Term 2, Term 3 for Year 11, 12 and 13 and Term 4 also for Year 9 and Year 10).
2. Exam Orders - grades obtained by students in each subject during their mock exams (Term 3 for Year 11, 12 and 13 and Term 2 and Term 4 for Year 9 and Year 10)

The Dux in Year 13 is calculated as follows:

1. In each Term Order, take the 4 top subject scores of each student
2. In the Term 3 Mock Exam, take the 4 top subject scores of each student

Total Score = Term 1 Total + Term 2 Total + Term 3 Total + Mock Exam Total * 2.5

The heavy weighting on mock exams requires consistent execution to achieve Dux. Many mock exams at King’s College are also based on past papers so students competing for Dux typically prepare by studying many or all of the prior exams in subjects like Physics, Further Mathematics, Economics, Biology and Chemistry.

An important factor in determining Dux is the maximum scaled score one can obtain in each subject. At King’s for the last 10 years, virtually every Dux has taken science-based subjects because the school’s internal scaling system rewards these subjects with a higher maximum scaled score (typically 96/100) compared to humanities subjects like business studies (top score can be 85/100 or worse sometimes).

For the last few years, most winners of Dux have pursued Further Mathematics, Biology, Chemistry, Physics, English Literature and a language or some combination of the above given their favorable scaling.