(Britain)(Australia) The top academic student in a school, or in a year of school; the top student in a specified academic discipline.
1849, Wilhelm Steven, The History of the High School of Edinburgh, page 191,
[…] on the motion of Sir John Marjoribanks, Bart., Lord Provost, unanimously resolved, July 27, 1814, “that there be annually presented by the town of Edinburgh to the boy at the head of the Greek class, taught by the rector of the High School, a gold medal of the same value [five guineas] as that annually presented to the dux of the Latin class.”
He finished the year dux of Form III with an average 90 per cent over eight subjects. The school did not award end-of-year marks in fourth and fifth forms, but Evans′ report for those years shows he passed all subjects in both years and was again dux in Form V.