Dear student,

If you have good command over your 11th and 12th syllabus and to the level of JEE specially then it will be not be a deal to crack IAT exam.

You can study for the IISER aptitude test using the same books that you used for JEE preparation. NCERT + coaching material particularly for Mathematics is a good mix. To pass the IAT, you must have a solid comprehension of ideas. Continue to practise conceptual questions.

In case If you have already studied in JEE advanced or NEET tutoring while preparing for JEE, simply use the supplements provided by your institute to answer current JEE advanced previous year questions and it will be good boost to your preparation.

Now here i cannot mention you the names of private coaching institutes as they promote themselves on lot of basis and we can be illusioned easily so better you can search for the coaching yourself by taking reviews of the students from the coaching.

To know more about this, you can go through the link below.

https://engineering.careers360.com/articles/iiser-admission

I hope this information helps you.

All the very best!!