Hello tanuja.. Hope you are doing well!!

You have got very good marks in your 12 board exams. I heartly congratulate you. Coming to your question getting seat in NIT is not about scoring good marks in 12th, it's all about jeemains and advance exams. You have to first qualify in jee mains exam with a good percentile to get seat in NIT's.

If you have any doubts regarding this you can ask in the comment section I'll be there to answer them.

Hope this helps you..

All the Best!!