I have been giving advice for musical topic term papers for years, and I tell you what I always say: you can do everything and the opposite of everything. The possible musical and musicological topics are hundreds, if not thousands, and the classical high school (liceo classico) is the track that most allows for interesting connections (I know because I did it too).
But, as when writing a real university thesis, it is always better to narrow down the topic. Narrow it down almost excessively, because it takes no time at all to broaden it again. For this reason, it is better to focus on a single author, or a single work, or a single musical topic.
As for school subjects, there can be many approaches. There are those who prefer to touch upon every subject, those who prefer to dedicate themselves to the "strong" subjects (and in the classical track, that would mean Italian, Latin, and Greek), those who focus on their "own" strong subjects (the ones you like most, basically), and those who, in an original but very wise way, focus on their weak subjects (because if you are doing poorly in physics but write a good paragraph about physics in your term paper, you have covered your tracks and avoided embarrassment).
So, the things I advise you to understand as soon as possible are:
1) which musical topics you prefer, know best, or would like to deal with. You mentioned Ligeti; does that mean you know him? Do you have a secret passion for Mozart, for his concertos, or for his chamber music with piano? Or instead, do you like the mechanics of the instrument? Opera? Rock? Up to you, basically.
2) which school subjects you know best and what the situation at school is like... for example, which teachers are good and which are less good and, above all, which subjects you think you can delve into without wanting to slit your wrists after two days. Keep in mind that the most difficult subjects to incorporate into a musical discussion in the classical track are Latin and Greek (especially Latin). This brings us to the tactics I mentioned before... if Latin literature speaks little or poorly of music, then it means you could eliminate it entirely from the term paper. Or, on the contrary, you could bring 4 lines of classical text specifically, outside the curriculum, to demonstrate that you are a tough student who isn't afraid to translate something extra (and regarding musical themes, there are especially things from Late Antiquity... if you bring 4 lines of Boethius on music to your final exams, and your teacher knows it and emphasizes it enough, the committee will give you a standing ovation).
3) extra-curricular and extra-musical passions. Suppose you are passionate about fashion; suppose you are passionate about Japanese manga; suppose you volunteer, or play tennis, or collect Barbies. Everything counts! Take every one of your interests into consideration, because many of them could be an interesting and original starting point for a great term paper.
At the bottom: obviously, if you want, you can contact me privately. I imagine it is the same for others writing on this forum.