Hello Jigyasha, Greetings!
So basically according to my knowledge ISRO requires Mathematics as a subject in your 10+2 score. The fact that you are a PCB student sounds like it is a bit difficult for you to get into ISRO. But nothing's impossible right? You can apply for the ISAT exam which is the entrance exam for IIST. Also, ISRO recruits people having atleast a graduation degree.
Hope this helps you. Good luck with your future.
Feel free to ask any more queries that trouble you.
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