Hello,
Your son have to appear for jee mains and jee advanced after class 12th board exam and try to score more than 70% of total marks in jee advanced to get admission in top IITs in aeronautical engineering branch.Your son can appear for jee advanced only if he crosses jee mains cutoff.It's cutoff varies every year but tell him to score 150+ out of 360 marks in jee mains.This will help him in getting some good private colleges.
If your son wants admission in aerospace engineering branch,then SRM UNIVERSITY can be the good choice too.For this he have to appear for an entrance exam called SRMJEEE. Other good options are MANIPAL INSTITUTE,UPES,P.E.C COLLEGE....
First let him clear his 10th and 12th with good marks i.e more than 75%...
You can get to know all details regarding exams and cutoff on our careers 360 website.
Good luck.