It sounds stupid, but you will simply do better in subjects that you love. If you love Theatre then take it, have fun do well. Look at all the statistics in life and those that do well, follow what they love - whether that is Art, Music, Physics or Computer Science it does not matter. Also remember you do not really know what you are going to be doing in the future - How is that a real job?’ Parents struggle to keep up with children’s career options
Doing subjects just because you wish to be challenged can be a bad choice. For example to study Medicine in the UK you do not need Math's HL but need to get 38 points and high points in Biology and Chemistry. SOOOOO choose Math's SL and focus on those other subjects to guarantee the grades!
The triangle of choosing a subject - is a sound model to follow do I NEED it for University (my University requires it), do I ENJOY it and AM I ACADEMICALLY GOOD at it. If all three are in place for a particular subject then it is a no brainer - simple!
Choosing an Arts subject if you are good at it and enjoy it is a great thing. Universities especially in the US love such variety, and it develops excellent skills. This is especially true of Theatre, which often students decided not to do and do another academic subject when in fact they would enjoy Theatre much more and Universities love it just as much as that supposedly "more academic" subject.
I know I know - this goes against the "Do what you love" but there are sometimes when choosing a subject you find easy creates balance in your IB. I have had the Geography discussion many times - and trust me it always works, Geography is a slightly easier IB course, and if you know you are good at it - then DO IT!
Yes your parents have a say, but it is your life and your studies so take control of them. Take advice, but then through research and a passion for what you want to do convince parents you are in control!
AND parents if you are reading here is some advice regarding how to support your son/daughter choosing the correct options and career without being too overbearing - remembering you can be successful in any career if you love it! -Washington Post article - How to help your child choose the right career, without being overbearing .
Yes to study Economics at the London School of Economics you need HL Math Analysis and Approaches - but this is only one University, there are many where you do not need Math HL and might fit in better? Remember if a University is asking for Math's HL the course is going to be full of Math's is that what you really want?
The more research you do, the more people you talk to - then the better decision you will make. Remember the IB Diploma, IB Courses and IB Careers pathways can be fun and joys to study if you have made the correct options choices. Conversely it can be a NIGHTMARE if you have not. Which will you choose?