B Schools focus on overall profiles rather than individual parameters. Individually speaking your 12th score values a lot in ISB Hyderabad admission. But if you look at the bigger picture it is just one of the many factors that determine one’s eligibility. B Schools specially ISB Hyderabad prefer candidates with an overall pleasing profile rather than extraordinary performance in one area only. For instance, someone with splendid past academics may not get admission because he wrote a poor essay or performed badly at the interview.
If you are bothered a lot by your low marks in class 10 or 12, you should have a logical reason for your poor performance. Also, you should compensate for poor scores by getting excellent GMAT scores and working on other areas like EQ and IQ. Another way to compensate for average past performance is by portraying an excellent extracurricular background or the social work you have done so far.
The most crucial part is the clarity of goals. More than any score what matters is the reason you choose MBA and that too from ISB Hyderabad.
Your profile should have something that sets you apart from other candidates and increases your chances of admission.