Hey Abhishek, if your son has applied from general category then it is impossible to get into any NIT with 80 percentile as at this percentile his expected rank will be about 1.7 lakh which I have calculated using the formula mentioned below.

{100-(percentile)}*8744.69

So, I would suggest you motivate him to try and improve his percentile in the coming April session of Jee mains.

Hope I made my self clear.

For details about previous year cut offs of NITs you can visit the link below:

https://engineering.careers360.com/articles/jee-main-cutoff