Polytechnic is basically diploma course after class 10th.
Comprises of 3 years as against science stream which is of 2 years.
Neuther do IITs or NITs accept diploma specialisation students.
IITs shall require science stream students with jee majn and jee  advanced both exams.
For NITs, jee main is enough.

Polytechnic shall fetch admission into second year of engineering directly through aggregate scores obtained in 3 years of diploma.