Well for engineering branch entrance exams are important.And based on the boards marks your son is eligible for counselling in all collegs along with IIT s..NIT s and GFITs.Now the best collegs in Tamil nadu are..Indian Institute of Technology, Madras.,National Institute of Technology Tirucherappalli,Alagappa College of Technology, Chennai,Government College of Technology, Coimbatore. .Madras Institute of Technology ,Chennai.