If you want to be a mobile app developer and if you want to start right now. Then go for COMPUTER SCIENCE dude!
They will teach you basic codings and stuff.
But you need to focus enough in this subject to be a coder. If you take science or commerce stream with this then do not give your entire time in subjects of science or commerce. You have to learn coding in such a way that you start loving it and it becomes your passion.
You can also check class 11 sumit arora's book and if you love the topics then you can surely go for it!
Also, your mind should be logical enough to understand the subject. Because if you get the logic it's great, if you don't it can be difficult for you!
So, go towards your passion!
App developer has an extremely bright future as each and every thing is getting digitalized!
Wish you luck! :)