Hello

It is not possible technically to do a Bachelors in Science from a recognised university when you have not passed your 12th standard yet. To be eligible for admission in any course in any colleg in India recognised by UGC you have to score atleas 40% marks in your boards.

Even so, to meet the eligibility criteria of kvpy you need to have svored a minimum of 60% in science subjects in your 12th standard. For more details on eligibilty for KVPY you can click on http://kvpy.iisc.ernet.in/main/eligibility.htm