most languages that aren't 'beginners' are some of the best scaling subjects you can do.
This is not exactly true. Beginners courses are, generally, very good scaling courses.
According to 2014 Table A3:
P90 Italian Beginners/French Beginners - scaled mark 40.6
P90 German Beginners - scaled mark 41.5
P90 Physics - scaled mark 42.0
P90 Modern History - scaled mark 39.9
P90 Biology - scaled mark 39.2
P90 English Advanced - scaled mark 41.7
P90 Japanese Continuers - scaled mark 42.9
P90 French Continuers - scaled mark 44.2
So, just from the data above, Beginners language courses are definitely not as good in terms of scaling as the Continuers courses. However, some Beginners courses do scale very well - almost as well as Physics.
(Other Beginners courses like Arabic don't scale well at all - no clue why).