Hello Shirish!

You must know that IISc is one of the most prestigious research oriented institutions in India. So, placements is actually not in your mind if you are interested in research. After completing BS degree in IISc, the higher studies trend is generalized amongst the graduates. And job opportunities do not increase before you complete your MS and Ph.D.

Right after your BS degree, you will be eligible for 1st year MS programme in IISc itself. If you pursue your masters' there, then you may apply for placements in The Office of Career Counselling and Placements (OCCaP). A rare percentage of graduates get placed in companies(ratio of about 2:83). It depends in which subject you completed your BS degree.

Because of the programmes STEM focus and duration (four years), there will be many opportunties for sure. If you want to work at Govt organizations, there are plently of opportunities in TIFR, ISRO, CCMB, NGRI etc. You work as a junior fellow scientist and can earn upto INR 55,000 per month(including allowances).

Otherwise, you have the option of pursuing direct Ph.D(without masters) or Integrated Ph.D/Masters in other Indian colleges and abroad. And finally work as a Research assistant or project assistant in leading institutes like the IITs, NITs, NISER and the IISERs.(You might have to give some additional exams in your fourth year like IIT JAM, CSIR-NET,etc.)

The research opportunities in abroad are immense. So, you can appear GRE and then TOEFL and get entrance into top universities in the USA.

There are other options for you too after your BS degree:-

1. Become a teacher in coaching institutes(both online and offline platform) or in schools after completeing BEd degree.
2. Become a professor in top Indian colleges
3. Appear CAT and go to IIM for pursuing MBA. This will open up many employment options for you.
4. Appear UPSC and join civil service.
5. Start your own company as an entrepreneur.

All the best!