Dear Suraj,

In order to be qualify for engineering entrance exam you should complete your 12th class or you must be appearing.

Eligibility criteria varies as per the entrance exam.

To take admission in IITs/NITs/IIITS and GFTIs you should have 75% marks in your 12th class or you should be in top 20 percentile.

For SC/ST it is 65% marks. 

Good luck!!