That depends on your cohort's performance in either the English Standard or English Advanced HSC exams, which is due to the moderation process. It is considered difficult to achieve a band 6 as your HSC mark (final mark) in English Standard, whereas it may not be as difficult to achieve the same result in English Advanced due to the advantage of alignment. For example, in the case of first rank in English Advanced as your final rank, your Assessment Mark will be adjusted to equal the highest Examination Mark (HSC exam mark) of any student in your cohort. While this may sound good, the limitation is that the highest mark may not be as high as you want it to be (i.e. it may not be a band 6 and higher). In such a case, having an average rank in English Advanced may be more beneficial. With that said, it is important that you do your utmost to maximise your rank, irrespective of whether you take English Standard or English Advanced.
I'm not entirely sure as to the reason behind your school's recommendations in terms of which subjects to take, except perhaps in the case of maths, where some university degrees have prerequisites (such as Mathematics Advanced as mentioned above). When I enrolled at my school, it was ranked in the 150's and I don't recall any recommendations of the sort. It was rather students who were in control of which subjects they wish to take and keep (with the exception of Mathematics Extension 2 perhaps). At the end of the day, encouraging or discouraging students from taking a particular subject remains a mere suggestion/recommendation from the school
I hope this helps!