It all depends on what career you're opting for. If you want to pursue some medical courses like MBBS, BAMS, BHMS, BPT, BVSC then you need the qualifying marks in 12th board exams which is around 60% marks only. And the exam that will decide your admission will be only NEET entrance exam. If you want to choose Engineering, then CET, JEE exams decide your future. And similarly, if you want to opt for BSC courses, then surely 12th boards marks will help you.

Kindly feel free to ask in the comments section about what actually you are aiming for and thus I can guide you in a much better way.

Thank you. Best wishes.