The students of IIST gets the maximum opportunity to get into ISRO. Also there are not such a rigorous interview to get a job in ISRO if you are student of IIST. You just keep in mind that you must secure a  CGPA of 8.5 or greater in order to be eligible for it. Keep on building the concepts and the skills, and you will not face any problem getting into ISRO.

To know more about IIST visit the link below:

https://www.careers360.com/university/indian-institute-of-space-science-and-technology-thiruvananthapuram

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