H Shreya 

If you have a plan to pursue BS(its B.S not Bsc)  from IISC bangalore you must be clear with the process that is,there are three ways by which you can get it.

1.KVPY(Kishor Vagyanik Protsahan Yojna first phase in class 11 2nd in class 12).

2.IIT-Jee(Advance)

3.IIT-Jee(Mains)

You can prepare for these exams and try to score good rank so that you can get IISc.

All the best.