IISc is the most prestigious institution in India for the students who are interested in Basic Sciences and Research. Thus to be a part of premiere institution it will need a lot of efforts. Now its dependent on the course in which you take admission in.

For Integrated BS-MS:

For this course you need to qualify the JEE advanced or the KVPY exam in order to be a part of the institution. As you know JEE Advanced is a tough exam as well as KVPY is a moderate exam with a interview (which is quite tough).

For Integrated MSc-PhD:

For this course you have to crack IIT JAM or JEST in order to get admission in this course after your BSc. This also will be followed by an interview.

Thus the general answer is yeah! Its tough to get into IISC but if you are interested in the subject and you have clear concepts as well as creative. Then IISc is a place esepecially for you and you will get a chance there

To know more about JEE Mains visit the link below:

Jee mains career360

To know more about JEE advanced visit the link below:

https://engineering.careers360.com/exams/jee-advanced

To know more about KVPY visit the link below:

https://school.careers360.com/exams/kvpy

To know more about IIT JAM visit the link below:

https://university.careers360.com/articles/jam

To know more about JEST visit the link below:

https://engineering.careers360.com/news/joint-entrance-screening-test-jest

I hope my answer helps. All the very best for your future endeavors!