It is mandatory that the candidates must secure 75% or more in 12th class or must be in the top 20 percentiles in the 12th class examination conducted by respective Boards.

For SC/ST category candidates there is a reservation for 105 marks. Qualifying marks for SC/ST candidates are 65% in the 12th class examination for IIT/NIT/IIIT/GFTI.

Therefore, you must fulfill the percentage criteria to become eligible to get admission into IIT/NIT/IIIT/GFTI even after clearing JEE Advanced .

From this session, Candidate should have secured at least 75% marks in the 12th class examination, or be in the top 20 percentile in the 12th  class examination conducted by the respective Boards. For SC/ST candidates the qualifying marks would be 65% in the  12th class examination for IIT/NIT/IIIT/GFTI .

So You need to fulfill above eligibility criteria to make eligible for IIT/NIT/IIIT/GFTI then after you need to secure good marks/rank in JEE Main to get admission in above institutions.

Please specify your 12th board percentage and board name?