I got 315mark in 12th std this year.I have interested to join NIT.
As you say that you got 315 marks in class 12 th this is 63 % marks.
For getting in touch with nit you have crosse the elligiblity criteria .
Elligiblity criteria are you have minimum 75 % marks in 12 th board in cbse or top 20 percentile in state board .
You have to improve your marks for nit, you can improve by giving improvement exam.
Best if luck