Logged in just so I can reply, I go to a very, very bad school as well. They refuse to buy textbooks and stuff for us simply because we have a Distance Education course. The facilities and teachers are mostly awful bar a few amazing teachers. I currently go to a Public school that focuses way to much on our feelings and programs to help apprenticeships.
One Thing I need to clarify and hope you see this. I am pretty sure the school is unable to force you into a subject. I have heard of people that have contacted the Department of Education and forced the school to move them or let them do a subject. So unless it is just a private school thing you should be able to stay in Mathematics and unless you are like rock bottom of the class I recommend it since general 2 is really easy.
To cope with my school and the people in it ive begun self teaching subjects, picked up the habit in year 10 when I began teaching a quarter of the top math class of my year since we were given an unqualified sub to teach us the work, who couldnt do it himself. This has become so useful, I can prepare for lessons and then take a few notes before zoning out since I know most of it.
Other then that I have simply learned to focus on me and furthering my own success, doing as well as you can and constantly asking for help from the teachers that you do like and if you are apart of or know friends apart of any sort of council or student body. Get them to bring it to the school. It kinda depends on what the problem is I guess. Music to study helps a lot I found with drowning out the problems in your classroom.
I didn't have that good of a teacher for chemistry (He tried but he wasn't exactly a chemistry teacher, he taught bio for years and then randomly the school made him chemistry teacher since the other teacher left previous year). I guess one thing you could do is get tutoring, but if you don't want to or can't do that, then what I found worked well for us in that chemistry class was to work with like a group of 4 or 5 students from the class that I would study with (like sharing good questions and answers to those questions), and the rest we had like a group chat where they could ask the higher ranking students questions, and since I was 1st I gave them my notes for free to try and help them out and pull up the class average so that everyone's marks improved. Pretty much did that in physics too (had a good teacher though) and we were able to get the highest % of band 6s to students in the class in both subjects because we worked together and most of both classes got above a band 5 apart from maybe 2 or 3 people
I have a similar situation with my teachers, where my physiscs teacher for all of prelim gave us a worksheet a week and missed soo much content, so we just got a group of friends (the 6 of us who all do similar classes and have the top 4 students in our year) and we just bounce ideas and use various textbooks and help each other.