First thing first, does your son or you feel that the NIT you are in is not delievering to you? if yes or either no, i wont recommend you to change a college. if the environment is not good along with education and placements then you can consider it otherwise its a no no but you can still try for an IIT and thats with JEE ADVANCE score. moreover if you are getting into an average iit then also you should not go into that and waste your year. i cannot give you the example here but the answer can be more simplified if you can mention the name of NIT your SON is into.

You can ask any query if you have one. I hope this helps. thanks.

Hello.

Admission into IIT is based only on Jee Advanced ranking and not Jee mains score. Your ward can attempt the exam for 3 years after completion of 12th, so if your ward meets this requirement, then they can attempt Jee mains, try to get qualified for Jee Advanced through which they can try to get into IIT.

Good luck!