If you want to become a Judge then you need to go for the studies of Law. Now law can be studied for any student background such as from Science, Arts & Commerce. So you have free will to choose but after your 12th you can join Integrated LLB or after your Graduation you can join LLB course. After LLB you have to do the LLM course.

Now if you want to choose subjects in your 10+2 then you can keep subjects such as Political Science, Legal Studies. This course can help you laterwards, else you can choose any subject of your choice and you can prepare as per the syllabus of CLAT entrance examination which is a broad entrance for LLB & Intergrated LLB course all over India.

For more information regarding Law entrances you can consider the link below:

https://law.careers360.com/

IF you want to know how to be a Judge you can consider the link below:

https://www.careers360.com/careers/judge

I hope this helps. Wish you a great eve!