In order to take admission in NITs/IITs/IIITs abd GFTIs you should have 75% marks in your boards exam or you should be in top 20 percentile.

If you are taking a drop you should go for improvement exam of class 12. So, that you can be eligible for these institutes. You should be determined and self motivated to get admission in good college.

On the basis of your 12th class marks you will be eligible for state level colleges and private colleges.

Also, if you are not willing to repeat 12th then there are some private colleges/universities which take admission through jee main, you can apply to those colleges.

To get admission in NITs/IIITs/GFTIs, 75% should be there in 12th or you should be there top 20 percentile. But you can go for DTU/NSIT with this percentage along with private colleges like VIT, SRM,Manipal etc. So dont get upset and try for rest choices. For more information, you can go through the below provided jee main eligibility criteria -

Jee Main Criteria

Good Luck!!!!