Somewhat your graduation score is very important to get Top B-School.Most of the Top management institutions consider the scores of your other classes.Other B Schools put a mandatory criteria that they will entertain the student who got more than 50 % in their graduation.
The graduation marks show your knowledge and skills in the subject. They count at the time of employment and at the time of admission for higher studies in India and abroad. Although most of the admissions happen on the basis of score in the entrance exam, however some of the reputed institutes also consider merit. Hope this clears your doubts. Good Luck!