Thanks for the question.

Since many students join the iiser viaJoint Entrance Examination of Indian Institutes of Technology (JEE) channel, hence coaching institutes such as aakash, bansal and vidyamandir classes are good ones.

If you want to get into iiser via kyvp, these are the good institutes - 

Sourav Sirs Classes

Gurukul Academy of Competitive Examination

Tutorcomp - Kolkata

All the best