I have the same problem. I am currently doing engineering studies and I dont really like it. Modern History is on the same line and I want to change to that because I love history. Problem is the class is full, however the head teacher said she would put me on the priority list so that if anyone drops that class, I will get to go straight into it. Perhaps you could negotiate with the teacher who organises this to put you on a waiting list or priority list so that if anyone drops legal studies, you can then pick it up.
I totally feel for you though, it sucks having to sit through a class you dont enjoy. I actually really wanted to do software design and development...but get this.. even though my school is a 'technology' school they didnt end up running it because there "wasnt enough people" and i know alot of people who chose it....yet engineering studies has what, 10? so angry at the school
so i was sort of forced to pick engineering studies because at the time I was already doing ancient history and didnt want to have two history subjects, but then this year I dropped ancient history for multimedia and I'm trying to get out of engineering for modern history. Apparently theres like 2 girls in the class who hate modern history and are trying to change...hopefully they drop it so i can get in >.<