There are two time-tested methods to determine the same :
Ask phone numbers of a few students studying currently in the Institute.Talk to them and ascertain the quality of teaching,
testing and broad guidance offered.
Find out the success ratio of the Institute i.e.find out how many students in the past few years have cleared the JEE exam out of how many students coached.Ask the phone numbers of a few students and interact with them and their parents.
Only
if you are satisfied on both the counts,
you may enroll in the Institute.