Your school was like oh no you can't do 5? My school was like oh no you can't do 4! Even though I'll have 7 total subjects coz I did 2 this year. Apparently 4 is too little and we'd get lazy from not having enough to do 
Yeah with those friends I was referring to before, many of them go to an infamous grammar school lol

(but apparently get the most 50 study scores in the state). It's the 'norm' in their school to do 1 in year 11 and 5 in year 12, even students that do 2 3/4s in year 11 still do 5 in year 11 even though they did very well in the year 11 3/4s (47+). I also know of two people that did six subjects in year 12, one did a year 11 3/4 and the other didn't but still managed to get 45+ in all their subjects (maths, science, languages, english)

. I think the students chose to do that though as they really wanted to do the subjects they were doing, they weren't force to by the school. I think this happens more in non-public schools rather than public schools because of the limited funding per student, meaning that they can't do more that the 'set' number of subjects unless it's done outside of school like through uni extension or a language school.